Compositions and methods for treating and diagnosing cancer

ABSTRACT

The present invention relates to compositions and methods for characterizing, treating and diagnosing cancer. In particular, the present invention provides a cancer stem cell profile, as well as novel stem cell cancer markers useful for the diagnosis, characterization, prognosis and treatment of cancer and in particular the targeting of solid tumor stem cells.

This application claims benefit of U.S. Appl. No. 60/731,469, filed Oct.31, 2005, U.S. Appl. No. 60/731,465, filed Oct. 31, 2005, and U.S. Appl.No. 60/731,279, filed Oct. 31, 2005, each of which is incorporatedherein by reference in its entirety.

This invention was made with government support under Grant No.5P01CA07513606 awarded by the National Institutes of Health. TheGovernment has certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates to the field of oncology and providesnovel compositions and methods for diagnosing and treating cancer. Inparticular, the present invention provides novel cancer stem cellmarkers, including, for example, the Notch signaling pathway targetHes6; CEACAM6, a member of the glycophosphatidylinositol (GPI) anchoredimmunoglobulin superfamily that mediates intercellular interactions; andintracellular aldehyde dehydrogenases (ALDH) useful for the study,diagnosis, and treatment of solid tumors.

BACKGROUND

Cancer is one of the leading causes of death in the developed world,resulting in over 500,000 deaths per year in the United States alone.Over one million people are diagnosed with cancer in the U.S. each year,and overall it is estimated that more than 1 in 3 people will developsome form of cancer during their lifetime. Though there are more than200 different types of cancer, four of them—breast, lung, colorectal,and prostate—account for over half of all new cases (Jemal et al., 2003,Cancer J. Clin. 53:5-26).

Breast cancer is the most common cancer in woman, with an estimate 12%of women at risk of developing the disease during their lifetime.Although mortality rates have decreased due to earlier detection andimproved treatments, breast cancer remains a leading cause of death inmiddle-aged women. Furthermore, metastatic breast cancer is still anincurable disease. On presentation, most patients with metastatic breastcancer have only one or two organ systems affected, but as the diseaseprogresses, multiple sites usually become involved. The most commonsites of metastatic involvement are locoregional recurrences in the skinand soft tissues of the chest wall, as well as in axilla andsupraclavicular areas. The most common site for distant metastasis isthe bone (30-40% of distant metastasis), followed by the lungs andliver. And although only approximately 1-5% of women with newlydiagnosed breast cancer have distant metastasis at the time ofdiagnosis, approximately 50% of patients with local disease eventuallyrelapse with metastasis within five years. At present the mediansurvival from the manifestation of distant metastases is about threeyears.

Current methods of diagnosing and staging breast cancer include thetumor-node-metastasis (TNM) system that relies on tumor size, tumorpresence in lymph nodes, and the presence of distant metastases asdescribed in the American Joint Committee on Cancer: AJCC Cancer StagingManual. Philadelphia, Pa.: Lippincott-Raven Publishers, 5th ed., 1997,pp 171-180, and in Harris, J R: “Staging of breast carcinoma” in Harris,J. R., Hellman, S., Henderson, I. C., Kinne D. W. (eds.): BreastDiseases. Philadelphia, Lippincott, 1991. These parameters are used toprovide a prognosis and select an appropriate therapy. The morphologicappearance of the tumor may also be assessed but because tumors withsimilar histopathologic appearance can exhibit significant clinicalvariability, this approach has serious limitations. Finally assays forcell surface markers can be used to divide certain tumors types intosubclasses. For example, one factor considered in the prognosis andtreatment of breast cancer is the presence of the estrogen receptor (ER)as ER-positive breast cancers typically respond more readily to hormonaltherapies such as tamoxifen or aromatase inhibitors than ER-negativetumors. Yet these analyses, though useful, are only partially predictiveof the clinical behavior of breast tumors, and there is much phenotypicdiversity present in breast cancers that current diagnostic tools failto detect and current therapies fail to treat.

Prostate cancer is the most common cancer in men in the developed world,representing an estimated 33% of all new cancer cases in the U.S., andis the second most frequent cause of death (Jemal et al., 2003, CACancer J. Clin. 53:5-26). Since the introduction of the prostatespecific antigen (PSA) blood test, early detection of prostate cancerhas dramatically improved survival rates, and the five year survivalrate for patients with local and regional stage prostate cancers at thetime of diagnosis is nearing 100%. Yet more than 50% of patients willeventually develop locally advanced or metastatic disease(Muthuramalingam et al., 2004, Clin. Oncol. 16:505-16).

Currently radical prostatectomy and radiation therapy provide curativetreatment for the majority of localized prostate tumors. However,therapeutic options are very limited for advanced cases. For metastaticdisease, androgen ablation with luteinising hormone-releasing hormone(LHRH) agonist alone or in combination with anti-androgens is thestandard treatment. Yet despite maximal androgen blockage, the diseasenearly always progresses with the majority developingandrogen-independent disease. At present there is no uniformly acceptedtreatment for hormone refractory prostate cancer, and chemotherapeuticregimes are commonly used (Muthuramalingam et al., 2004, Clin. Oncol.16:505-16; Trojan et al., 2005, Anticancer Res. 25:551-61).

Lung cancer is the most common cancer worldwide, the third most commonlydiagnosed cancer in the United States, and by far the most frequentcause of cancer deaths (Spiro et al., 2002, Am. J. Respir. Crit. CareMed. 166:1166-96; Jemal et al., 2003, CA Cancer J. Clin. 53:5-26).Cigarette smoking is believed responsible for an estimated 87% of alllung cancers making it the most deadly preventable disease. Lung canceris divided into two major types that account for over 90% of all lungcancers: small cell lung cancer (SCLC) and non-small cell lung cancer(NSCLC). SCLC accounts for 15-20% of cases and is characterized by itsorigin in large central airways and histological composition of sheetsof small cells with little cytoplasm. SCLC is more aggressive thanNSCLC, growing rapidly and metastasizing early and often. NSCLC accountsfor 80-85% of all cases and is further divided into three major subtypesbased on histology: adenocarcinoma, squamous cell carcinoma (epidermoidcarcinoma), and large cell undifferentiated carcinoma.

Lung cancer typically presents late in its course, and thus has a mediansurvival of only 6-12 months after diagnosis and an overall 5 yearsurvival rate of only 5-10%. Although surgery offers the best chance ofa cure, only a small fraction of lung cancer patients are eligible withthe majority relying on chemotherapy and radiotherapy. Despite attemptsto manipulate the timing and dose intensity of these therapies, survivalrates have increased little over the last 15 years (Spiro et al., 2002,Am. J. Respir. Crit. Care Med. 166:1166-96).

Colorectal cancer is the third most common cancer and the fourth mostfrequent cause of cancer deaths worldwide (Weitz et al., 2005, Lancet365:153-65). Approximately 5-10% of all colorectal cancers arehereditary with one of the main forms being familial adenomatouspolyposis (FAP), an autosomal dominant disease in which about 80% ofaffected individuals contain a germline mutation in the adenomatouspolyposis coli (APC) gene. Colorectal carcinoma has a tendency to invadelocally by circumferential growth and elsewhere by lymphatic,hematogenous, transperitoneal, and perineural spread. The most commonsite of extralymphatic involvement is the liver, with the lungs the mostfrequently affected extra-abdominal organ. Other sites of hematogenousspread include the bones, kidneys, adrenal glands, and brain.

The current staging system for colorectal cancer is based on the degreeof tumor penetration through the bowel wall and the presence or absenceof nodal involvement. This staging system is defined by three majorDuke's classifications: Duke's A disease is confined to submucosa layersof colon or rectum; Duke's B disease has tumors that invade throughmuscularis propria and can penetrate the wall of the colon or rectum;and Duke's C disease includes any degree of bowel wall invasion withregional lymph node metastasis. While surgical resection is highlyeffective for early stage colorectal cancers, providing cure rates of95% in Duke's A patients, the rate is reduced to 75% in Duke's Bpatients and the presence of positive lymph node in Duke's C diseasepredicts a 60% likelihood of recurrence within five years. Treatment ofDuke's C patients with a post surgical course of chemotherapy reducesthe recurrence rate to 40%-50%, and is now the standard of care forthese patients.

Epithelial carcinomas of the head and neck arise from the mucosalsurfaces in the head and neck area and are typically squamous cell inorigin. This category includes tumors of the paranasal sinuses, the oralcavity, and the nasopharynx, oropharynx, hypopharynx, and larynx.

The annual number of new cases of head and neck cancers in the UnitedStates is approximately 40,000 per year, accounting for about 5 percentof adult malignancies. Head and neck cancers are more common in someother countries, and the worldwide incidence probably exceeds half amillion cases annually. In North American and Europe, the tumors usuallyarise from the oral cavity, oropharynx, or larynx, whereas nasopharynealcancer is more common in the Mediterranean countries and in the FarEast.

Traditional modes of therapy (radiation therapy, chemotherapy, andhormonal therapy), while useful, have been limited by the emergence oftreatment-resistant cancer cells. Clearly, new approaches are needed toidentify targets for treating head and neck cancer and cancer generally.

Cancer arises from dysregulation of the mechanisms that control normaltissue development and maintenance, and increasingly stem cells arethought to play a central role (Beachy et al., 2004, Nature 432:324).During normal animal development, cells of most or all tissues arederived from normal precursors, called stem cells (Morrison et al.,1997, Cell 88:287-98; Morrison et al., 1997, Curr. Opin. Immunol.9:216-21; Morrison et al., 1995, Annu. Rev. Cell. Dev. Biol. 11:35-71).Stem cells are cells that: (1) have extensive proliferative capacity; 2)are capable of asymmetric cell division to generate one or more kinds ofprogeny with reduced proliferative and/or developmental potential; and(3) are capable of symmetric cell divisions for self-renewal orself-maintenance. The best-known example of adult cell renewal by thedifferentiation of stem cells is the hematopoietic system wheredevelopmentally immature precursors (hematopoietic stem and progenitorcells) respond to molecular signals to form the varied blood andlymphoid cell types. Other cells, including cells of the gut, breastductal system, and skin are constantly replenished from a smallpopulation of stem cells in each tissue, and recent studies suggest thatmost other adult tissues also harbor stem cells, including the brain.

Solid tumors are composed of heterogeneous cell populations. Forexample, breast cancers are a mixture of cancer cells and normal cells,including mesenchymal (stromal) cells, inflammatory cells, andendothelial cells. Classic models of cancer hold that phenotypicallydistinct cancer cell populations all have the capacity to proliferateand give rise to a new tumor. In the classical model, tumor cellheterogeneity results from environmental factors as well as ongoingmutations within cancer cells resulting in a diverse population oftumorigenic cells. This model rests on the idea that all populations oftumor cells would have some degree of tumorigenic potential. (Pandis etal., 1998, Genes, Chromosomes & Cancer 12:122-129; Kuukasjrvi et al.,1997, Cancer Res. 57:1597-1604; Bonsing et al., 1993, Cancer 71:382-391;Bonsing et al., 2000, Genes Chromosomes & Cancer 82: 173-183; Beerman Het al., 1991, Cytometry. 12:147-54; Aubele M & Werner M, 1999, Analyt.Cell. Path. 19:53; Shen L et al., 2000, Cancer Res. 60:3884).

An alternative model for the observed solid tumor cell heterogeneity isthat solid tumors result from a “solid tumor stem cell” (or “cancer stemcell” from a solid tumor) that subsequently undergoes chaoticdevelopment through both symmetric and asymmetric rounds of celldivision. In this stem cell model, solid tumors contain a distinct andlimited (possibly even rare) subset of cells that share properties withnormal “stem cells” in that they extensively proliferate and efficientlygive rise both to additional solid tumor stem cells (self-renewal) andto the majority of within a solid tumor that lack tumorigenic potential.Indeed, mutations within a long-lived stem cell population can initiatethe formation of cancer stem cells that underlie the growth andmaintenance of tumors and whose presence contributes to the failure ofcurrent therapeutic approaches.

The stem cell nature of cancer was first revealed in the blood cancer,acute myeloid leukemia (AML) (Lapidot et al., 1994, Nature 17:645-8).More recently it has been demonstrated that malignant human breasttumors similarly harbor a small, distinct population of cancer stemcells enriched for the ability to form tumors in immunodeficient mice.An ESA+, CD44+, CD24−/low, Lin− cell population was found to be 50-foldenriched for tumorigenic cells compared to unfractionated tumor cells(Al-Hajj et al., 2003, PNAS 100:3983-8). Furthermore, a similarpopulation is also present in colon cancers. The ability toprospectively isolate the tumorigenic cancer cells has permitted preciseinvestigation of critical biological pathways that underlietumorigenicity in these cells, and thus promises the development ofbetter diagnostic assays and therapeutics for cancer patients. It istoward this purpose that this invention is directed.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to compositions and methods in the fieldof oncology. In particular, the present invention provides a geneexpression profile associated with solid tumor stem cells each gene ofwhich provides a novel stem cell cancer marker. In certain embodiments acancer stem cell gene expression profile comprises genes differentiallyexpressed in cancer stem cells compared to unfractionated tumor cells.In other certain embodiments a cancer stem cell gene expression profilecomprises genes differentially expressed in cancer stem cells comparedto non-tumorigenic tumor cells, which comprise the majority of thetumor. The cancer stem cell markers identified by the present inventionare useful for the characterization, diagnosis, prognosis, and treatmentof cancer and in particular, targeting solid tumor stem cells within aparticular cancer.

The present invention provides an isolated population of cancer stemcells, for example colon or head and neck, obtained from the respectivetumor of epithelial origin, wherein the population comprises at least75% cancer stem cells, colon or head and neck, and less than 25% tumorcells, wherein the colon or head and neck cancer stem cells: aretumorigenic; and are CD44+ compared to non-tumorigenic tumor cells.

The present invention provides an enriched population of cancer stemcells, for example colon or head and neck obtained from the respectivetumor of epithelial origin, wherein the population comprises colon orhead and neck cancer stem cells and colon or head and neck tumor cells,wherein the cancer stem cells: are enriched at least two-fold comparedto unfractionated tumor cells; are tumorigenic; and are CD44+ comparedto non-tumorigenic colon tumor cells.

The present invention provides an isolated population of cancer stemcells, for example colon or head and neck, obtained from the respectivetumor of epithelial origin, wherein the population comprises at least75% colon or head and neck cancer stem cells and less than 25% colon orhead and neck tumor cells, wherein the colon or head and neck cancerstem cells: are tumorigenic; and express elevated levels of CD166compared to non-tumorigenic colon tumor cells.

The present invention provides an enriched population of cancer stemcells, for example colon or head and neck obtained from the respectivetumor of epithelial origin, wherein the population comprises colon orhead and neck cancer stem cells and colon or head and neck tumor cells,wherein the cancer stem cells: are enriched at least two-fold comparedto unfractionated tumor cells; are tumorigenic; and are CD166 comparedto non-tumorigenic colon tumor cells.

The present invention provides an isolated population of cancer stemcells, for example colon or head and neck, obtained from the respectivetumor of epithelial origin, wherein the population comprises at least75% colon or head and neck cancer stem cells and less than 25% colon orhead and neck tumor cells, wherein the colon or head and neck cancerstem cells: are tumorigenic; and express elevated levels of CD49fcompared to non-tumorigenic colon tumor cells.

The present invention provides an enriched population of cancer stemcells, for example colon or head and neck obtained from the respectivetumor of epithelial origin, wherein the population comprises colon orhead and neck cancer stem cells and colon or head and neck tumor cells,wherein the cancer stem cells: are enriched at least two-fold comparedto unfractionated tumor cells; are tumorigenic; and are CD49f comparedto non-tumorigenic colon tumor cells.

The present invention provides an isolated population of cancer stemcells, for example colon or head and neck, obtained from the respectivetumor of epithelial origin, wherein the population comprises at least75% colon or head and neck cancer stem cells and less than 25% colon orhead and neck tumor cells, wherein the colon or head and neck cancerstem cells: are tumorigenic; and express elevated levels of CD59compared to non-tumorigenic colon tumor cells.

The present invention provides an enriched population of cancer stemcells, for example colon or head and neck obtained from the respectivetumor of epithelial origin, wherein the population comprises colon orhead and neck cancer stem cells and colon or head and neck tumor cells,wherein the cancer stem cells: are enriched at least two-fold comparedto unfractionated tumor cells; are tumorigenic; and are CD59 compared tonon-tumorigenic colon tumor cells.

The present invention provides an isolated population of cancer stemcells, for example colon or head and neck obtained from the respectivetumor of epithelial origin, wherein the population comprises at least75% colon or head and neck cancer stem cells and less than 25% colon orhead and neck tumor cells, wherein the colon or head and neck cancerstem cells: are tumorigenic; are CD44+, and express elevated levels ofCD166 compared to non-tumorigenic colon tumor cells. In certainembodiments, the isolated colon cancer stem cells further express ESA.

The present invention provides an isolated population of cancer stemcells, for example colon or head and neck obtained from the respectivetumor of epithelial origin, wherein the population comprises at least95% colon or head and neck cancer stem cells and less than 5%non-tumorigenic colon or head and neck tumor cells, wherein the colon orhead and neck cancer stem cells are both tumorigenic and expresselevated levels of CD166 compared to non-tumorigenic colon tumor cells.

The present invention provides an isolated population of colon cancerstem cells obtained from a colon tumor of epithelial origin, wherein thepopulation comprises at least 75% colon cancer stem cells and less than25% colon tumor cells, wherein the colon cancer stem cells: aretumorigenic; and express elevated levels of one or more of PTGFRN,CD166, CD164, CD82, TGFBR1, MET, EFNB2, ITGA6, TDGF1, HBEGF, ABCC4,ABCD3, TDE2, ITGB1, TNFRSF21, CD81, CD9, KIAA1324, CEACAM6, FZD6, FZD7,BMPR1A, JAG1, ITGAV, NOTCH2, SOX4, The present invention provides anisolated population of cancer stem cells obtained from a tumor ofepithelial origin, wherein the population comprises at least 75% cancerstem cells and less than 25% tumor cells, wherein the cancer stem cells:are tumorigenic; are CD44+; and express elevated levels of one or moreof PTGFRN, CD166, CD164, CD82, TGFBR1, MET, EFNB2, ITGA6, TDGF1, HBEGF,ABCC4, ABCD3, TDE2, ITGB1, TNFRSF21, CD81, CD9, KIAA1324, CEACAM6, FZD6,FZD7, BMPR1A, JAG1, ITGAV, NOTCH2, SOX4, HES1, HES6, ATOH1, CDH1, EPHB2,MYB, MYC, SOX9 or STRAP, or lower levels of one or more of TCF4 or VIM,compared to non-tumorigenic tumor cells. In certain embodiments, theisolated cancer stem cells further express ESA. In certain embodiments,the isolated cancer stem cells are colon cancer stem cells. In certainembodiments, the isolated cancer stem cells are head and neck cancerstem cells.

The present invention provides an isolated population of cancer stemcells obtained from a tumor of epithelial origin, wherein the populationcomprises at least 95% cancer stem cells and less than 5%non-tumorigenic tumor cells, wherein the cancer stem cells: aretumorigenic, are CD44+, and express elevated levels of one or more ofPTGFRN, CD166, CD164, CD82, TGFBR1, MET, EFNB2, ITGA6, TDGF1, HBEGF,ABCC4, ABCD3, TDE2, ITGB1, TNFRSF21, CD81, CD9, KIAA1324, CEACAM6, FZD6,FZD7, BMPR1A, JAG1, ITGAV, NOTCH2, SOX4, HES1, HES6, ATOH1, CDH1, EPHB2,MYB, MYC, SOX9 or STRAP, or lower levels of one or more of TCF4 or VIM,compared to non-tumorigenic tumor cells. In certain embodiments, theisolated cancer stem cells further express ESA. In certain embodiments,the isolated cancer stem cells are colon cancer stem cells. In certainembodiments, the isolated cancer stem cells are head and neck cancerstem cells.

The present invention provides an enriched population of cancer stemcells obtained from a tumor of epithelial origin, wherein the populationcomprises cancer stem cells and tumor cells, wherein the cancer stemcells: are enriched at least two-fold compared to unfractionated tumorcells; are tumorigenic; are CD44+; and express elevated levels of one ormore of PTGFRN, CD166, CD164, CD82, TGFBR1, MET, EFNB2, ITGA6, TDGF1,HBEGF, ABCC4, ABCD3, TDE2, ITGB1, TNFRSF21, CD81, CD9, KIAA1324,CEACAM6, FZD6, FZD7, BMPR1A, JAG1, ITGAV, NOTCH2, SOX4, HES1, HES6,ATOH1, CDH1, EPHB2, MYB, MYC, SOX9 or STRAP, or lower levels of eitheror both of TCF4 or VIM, compared to non-tumorigenic tumor cells. Incertain embodiments, the enriched cancer stem cells further express ESA.In certain embodiments, the isolated cancer stem cells are colon cancerstem cells. In certain embodiments, the isolated cancer stem cells arehead and neck cancer stem cells.

The present invention provides an enriched population of cancer stemcells obtained from a tumor of epithelial origin, wherein the populationcomprises cancer stem cells and tumor cells, wherein the cancer stemcells: are enriched at least five-fold compared to unfractionated tumorcells; are tumorigenic; are CD44+, and express elevated levels of one ormore of PTGFRN, CD166, CD164, CD82, TGFBR1, MET, EFNB2, ITGA6, TDGF1,HBEGF, ABCC4, ABCD3, TDE2, ITGB1, TNFRSF21, CD81, CD9, KIAA1324,CEACAM6, FZD6, FZD7, BMPR1A, JAG1, ITGAV, NOTCH2, SOX4, HES1, HES6,ATOH1, CDH1, EPHB2, MYB, MYC, SOX9 or STRAP, or lower levels of eitheror both of TCF4 or VIM, compared to non-tumorigenic tumor cells. Incertain embodiments, the isolated cancer stem cells are colon cancerstem cells. In certain embodiments, the isolated cancer stem cells arehead and neck cancer stem cells.

The present invention provides methods for obtaining from a tumor acellular composition comprising cancer stem cells and non-tumorigenictumor cells, wherein at least 75% are tumorigenic stem cells and 25% orless are non-tumorigenic tumor cells, said method comprising: (a)obtaining a dissociated mixture of tumor cells from a tumor ofepithelial origin; (b) separating the mixture of tumor cells into afirst fraction comprising at least 75% cancer stem cells and 25% or lessnon-tumorigenic tumor cells and a second fraction of tumor cellsdepleted of cancer stem cells wherein the separating is by contactingthe mixture with one or more reagents, including for example CD44 andESA; and (c) demonstrating the first fraction to be tumorigenic byserial injection into a host animal and the second fraction to benon-tumorigenic by serial injection into the host animal. In certainembodiments the separating is performed by flow cytometry, fluorescenceactivated cell sorting (FACS), panning, affinity chromatography ormagnetic selection. In certain embodiments the separating is performedby fluorescence activated cell sorters (FACS) analysis.

The present invention provides methods for obtaining from a tumor acellular composition comprising cancer stem cells and non-tumorigenictumor cells, wherein at least 75% are tumorigenic stem cells and 25% orless are non-tumorigenic tumor cells, said method comprising: (a)obtaining a dissociated mixture of tumor cells from a tumor ofepithelial origin; (b) separating the mixture of tumor cells into afirst fraction comprising at least 75% cancer stem cells and 25% or lessnon-tumorigenic tumor cells and a second fraction of tumor cellsdepleted of cancer stem cells wherein the separating is by contactingthe mixture with reagents against CD44 and ESA; and (c) demonstratingthe first fraction to be tumorigenic by serial injection into a hostanimal and the second fraction to be non-tumorigenic by serial injectioninto the host animal. In certain embodiments the separating is performedby flow cytometry, fluorescence activated cell sorting (FACS), panning,affinity chromatography or magnetic selection. In certain embodimentsthe separating is performed by fluorescence activated cell sorters(FACS) analysis.

The present invention provides methods for enriching a population ofcancer stem cells from a tumor of epithelial origin wherein the enrichedpopulation comprises 75% cancer stem cells and 25% or lessnon-tumorigenic tumor cells, said method comprising: (a) obtaining adissociated mixture of tumor cells from a tumor of epithelial origin;(b) contacting the mixture of tumor cells with one or more reagents,including for example CD44 and ESA; (c) selecting a first fraction ofcancer stem cells by their binding to the reagents and a second fractionof tumor cells depleted of cancer stem cells; and (d) demonstrating thefirst fraction to be tumorigenic by serial injection of the tumor stemcells into a host animal and the second fraction to be non-tumorigenicby serial injection into the host animal. In certain embodiments theselecting is performed by flow cytometry, fluorescence activated cellsorting (FACS), panning, affinity chromatography or magnetic selection.In certain embodiments the selecting is performed by fluorescenceactivated cell sorters (FACS) analysis.

The present invention provides the means and methods for enriching apopulation of cancer stem cells from a colon tumor of epithelial originwherein the enriched population comprises 75% cancer stem cells and 25%or less non-tumorigenic tumor cells, said method comprising: (a)obtaining a dissociated mixture of tumor cells from a tumor ofepithelial origin; (b) contacting the mixture of tumor cells withreagents against CD44 and ESA; (c) selecting a first fraction of cancerstem cells by their binding to the reagents and a second fraction oftumor cells depleted of cancer stem cells; and (d) demonstrating thefirst fraction to be tumorigenic by serial injection of the tumor stemcells into a host animal and the second fraction to be non-tumorigenicby serial injection into the host animal. In certain embodiments theselecting is performed by flow cytometry, fluorescence activated cellsorting (FACS), panning, affinity chromatography or magnetic selection.In certain embodiments the selecting is performed by fluorescenceactivated cell sorters (FACS) analysis.

The present invention provides an isolated population of cancer stemcells obtained from a tumor of epithelial origin, wherein the populationcomprises at least 75% cancer stem cells and less than 25% tumor cells,wherein the cancer stem cells: are tumorigenic; are CD44+, and displayelevated levels of ALDH activity compared to non-tumorigenic tumorcells. In certain embodiments, the isolated cancer stem cells furtherexpress ESA. In certain embodiments, the isolated cancer stem cells arecolon cancer stem cells. In certain embodiments, the isolated cancerstem cells are head and neck cancer stem cells.

The present invention provides an enriched population of cancer stemcells obtained from a tumor of epithelial origin, wherein the populationcomprises cancer stem cells and tumor cells, wherein the cancer stemcells: are enriched at least two-fold compared to unfractionated tumorcells; are tumorigenic; are CD44+; and display elevated levels of ALDHactivity compared to non-tumorigenic tumor cells. In certainembodiments, the enriched cancer stem cells further express ESA. Incertain embodiments, the isolated cancer stem cells are colon cancerstem cells. In certain embodiments, the isolated cancer stem cells arehead and neck cancer stem cells.

The present invention provides a method of identifying the presence ofcancer stem cells in a subject suspected of having cancer, wherein themethod comprises: (a) obtaining a biological sample from the subject;(b) dissociating cells of the sample; (c) contacting the dissociatedcells with a first reagent that binds CD44 and a second reagent thatbinds CD166; and (d) detecting cancer stem cells that bind to the firstand second reagent. In certain embodiments, the first or second reagentis an antibody. In certain embodiments, the detection step is performedby flow cytometry, fluorescence activated cell sorting, panning,affinity column separation, or magnetic selection. In certainembodiments, the cancer stem cells are colon cancer stem cells. Incertain embodiments, the cancer stem cells are head and neck cancer stemcells.

The present invention provides a method of identifying the presence ofcancer stem cells in a subject suspected of having cancer, wherein themethod comprises: (a) obtaining a biological sample from the subject;(b) dissociating cells of the sample; (c) contacting the dissociatedcells with a first reagent that binds CD44 and a second reagent thatdetects ALDH activity; and (d) detecting cancer stem cells that bind tothe first reagent and that show increased ALDH activity. In certainembodiments, the first reagent is an antibody. In certain embodiments,the detection step is performed by flow cytometry, fluorescenceactivated cell sorting, panning, affinity column separation, or magneticselection. In certain embodiments, the cancer stem cells are coloncancer stem cells. In certain embodiments, the cancer stem cells arehead and neck cancer stem cells.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

FIG. 1: FACS Sorting of a Population of Tumor Cells Containing TumorStem Cell Activity. (A, B) Subpopulations of tumor cells from a humancolorectal cancer were passaged through immunodeficient mice, depletedof mouse-derived cells using anti-mouse H2K^(d) and CD45 antibodies, andisolated based on expression of ESA and CD44. Cells positive for bothcell surface markers (TG; top gate; red) are tumorigenic (see FIG. 2 &Table 2) and were compared by microarray analysis to non-tumorigeniccells (NTG; blue).

FIG. 2: ESA+44+ Colon Tumor Cells are Tumorigenic. ESA+44+ colon cancerstem cells (CoCSC) versus non-ESA+44+ colon tumor cells (Other) wereisolated by FACS and injected subcutaneously into immunodeficient miceat cell doses of approximately A) 1000 or B) 100 cells per animal. Mean±SEM tumor volume for each dose is plotted. After 80+ days, tumor volumecontinued to increase in mice injected with CoCSC but tumors neverdeveloped in mice injected with non-ESA+44+ colon tumor cells (Other).

FIG. 3: Tumors generated by Colon Cancer Stem Cells Retain theirPhenotypic Identity. A flow cytometry profile of colon tumor cells showsexpression of ESA and CD44 (left). ESA+44+ colon cancer stem cells areisolated (middle) by FACS and injected into immunodeficient mice. Whenthe tumors generated in mice from these purified CoCSC are reanalyzedfor the expression of ESA and CD44, the tumor phenotype is identical tothat of the original heterogeneous tumor (right).

FIG. 4: Genes Differentially Expressed in Colon Cancer Stem Cells. A)The fold relative expression of different genes, as determined bymicroarray analysis, in ESA+44+ tumorigenic (TG) colon cancer stem cellsversus non-tumorigenic (NTG) sorted tumor cells is graphed. B) Relativegene expression of targets was validated by Taqman quantitative RT-PCRusing FACS-purified TG versus NTG UM-C4 colon cancer cells. Results werenormalized versus an internal control (i.e. GUSB) prior to relativeexpression analysis.

FIG. 5: Differential Expression of Hes1 and Hes6 in Colon Cancer StemCells. The relative expression of different Hes genes in ESA+44+ coloncancer stem cells versus non-tumorigenic sorted tumor cells is shown. A)In contrast to HES2, 4 and 7, HES1 & 6 show increased expression incolon cancer stem cells versus non-tumorigenic sorted tumor cells. B)Relative expression of HES1 was validated by Taqman quantitative RT-PCRusing FACS-purified TG versus NTG UM-C4 colon cancer cells. Results werenormalized versus an internal control (i.e. GUSB) prior to relativeexpression analysis.

FIG. 6: Differential Expression CEACAM6 in Tumorigenic Colon Cells.Absolute expression by Affymetrix array analysis of CEACAM6 in ESA+44+colon cancer stem cells (TG) compared to non-tumorigenic tumor cells(NTG).

FIG. 7: Expression of CEACAM6 by Colon Tumor Cells. A) Flow cytometryanalysis of colon tumor cells, demonstrating expression profile ofCEACAM6. B) Flow cytometry profile of colon tumors, showing expressionof CD44 and CEACAM6 by ESA+ colon tumor cells. Roughly 62% of ESA+44+cells are also CEACAM6 positive.

FIG. 8: Expression of CD166 by Colon Tumor Cells. A flow cytometryprofile showing expression of CD44 and CD166 by ESA+ colon tumor cells.Roughly 94% of ESA+44+ cells are also CD166 positive.

FIG. 9: The Majority of CD44+ Cells have Elevated ALDH Activity. A)CD44/Aldefluor™ flow cytometry profile of mouse lineage-negative (mLin−;H2K^(d) and murine CD45), ESA+ xenogeneic UM-C4 and UM-C6 colon tumorcells in the presence or absence of the ALDH1 inhibitor, DEAB. Tumorgrowth curves are shown for the denoted FACS purified populations fromB) UM-C4 and C) UM-C6 tumors injected at a dose of 500 cellssubcutaneously. Means ±SEM are plotted and reflect only those mice withpalpable tumors.

FIG. 10: Relative ALDH Gene Family Expression. A) Absolute expressionlevels of ALDH family member mRNA as determined by Affymetrix microarryanalysis is shown. B) Inset shows the relative expression of severalALDH genes in TG versus NTG cells from different colon tumor xenografts.C) Inset shows relative expression of ALDH1A1 as validated by Taqmanquantitative RT-PCR using FACS-purified TG versus NTG cells. Resultswere normalized versus an internal control (i.e. GUSB) prior to relativeexpression analysis.

FIG. 11: Tumorigenic UM-C4 Cells Preferentially Survive CPAChemotherapy. A) Twice weekly administration of 25 mg/kg CPA resulted indelayed UM-C4 tumor growth versus control, vehicle-treated mice.Phenotypic analysis of residual tumors at day fifteen demonstrated B)higher concentrations of ESA+CD44+ cells and C) an increased percentageof cells with ALDH activity. D) Limiting dilution analysis ofunfractionated UM-C4 tumor cells demonstrated a significant increase intumorigenic cell frequency. E) Though ESA+CD44+ cells were equallytumorigenic, tumors were more aggressive when obtained from CPA comparedto control tumors.

FIG. 12: In Vitro Exposure to BMPs Reduces Tumorigenicity of UM-C6 coloncancer cells. Mouse lineage-negative (mLin−; H2 K^(d) and murine CD45)cells were plated on laminin-coated coverslips and cultured in thepresence of absence of 100 ng/mL BMP2 and BMP4 for 6 days, thenharvested and injected subcutaneously into mice to determinetumorigenicity. A) Tumor frequency is shown (in parentheses) for control(Med D) and BMP-exposed (BMP2/4) tumor cells and the Means ±SEM areplotted to reflect only those mice with palpable tumors. B) The finalmeasurement of all tumors at day 75 demonstrated a significant reductionin tumor growth following exposure to BMPs.

FIG. 13: Head and Neck Cancer Stem Cells. Shown are representative plotsrevealing the phenotypic diversity in tumors arising from CD44+Lin−cells in UMHN2. The plots depict the CD44 staining pattern of livecancer cells from (a) primary unpassaged tumor, (b) tumor resulting fromthe implantation of CD44+Lin− cells from the primary tumor (oncepassaged tumor) and (c) tumor resulting from the implantation ofCD44⁺Lin− cells from the once passaged tumor.

FIG. 14: Side population (SP) Enriches for Colon Cancer Stem Cells. A)SP phenotype cells (red) are enriched for colon cancer stem cellscompared to SP-intermediate cells (green) and non-SP cells (dark blue).B) Microarray analysis revealed that tumorigenic (TG) mouselineage-negative (mLin−), ESA+ xenogeneic UMC4 (C4), UMC6 (C6), andOMP-C9 (C9) colon tumor cells have elevated levels of ABC family membertransporter mRNA compared to non-tumorigenic (NTG) cells.

FIG. 15: CD59 Enriches for Colon Cancer Stem Cells. A) By microarray,tumorigenic (TG) mouse lineage-negative (mLin−), ESA+ xenogeneic UMC4,UMC6, and OMP-C9 colon tumor cells have elevated levels of CD59 mRNAcompared to non-tumorigenic (NTG) cells. B) Colon tumor cells haveelevated CD59 surface expression, which is preferentially found on CD44+cells. C) A tumor growth curve is shown for the denoted FACS purifiedpopulations from ESA+CD44+ cells further enriched based on CD59expression. Means ±SEM are plotted and reflect only those mice withpalpable tumors. Tumor frequency is shown in parentheses and in Table 4.

FIG. 16: CD49f (α6-integrin) Enriches for Colon Cancer Stem Cells. A)Mouse lineage-negative (mLin−), ESA+ xenogeneic UM-C4 colon tumor cellshave elevated levels of CD49f, and CD49f surface expression waspreferentially found on CD44+ cells. B) A tumor growth curves is shownfor the denoted FACS purified populations from ESA+CD44+ cells furtherenriched based on CD49f expression. Means ±SEM are plotted and reflectonly those mice with palpable tumors. Tumor frequency is shown inparentheses and in Table 4. Data is representative of N=2 separateexperiments.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to compositions and methods for treating,characterizing and diagnosing cancer. This invention is based on thediscovery of solid tumor stem cells (also referred to as cancer stemcells or cancer stem cells from a solid tumor) as a distinct and limitedsubset of cells within the heterogenous cell population of establishedsolid tumors. These cancer stem cells share the properties of normalstem cells in that they extensively proliferate and efficiently giverise both to additional solid tumor stem cells (self-renewal) and to themajority of tumor cells of a solid tumor that lack tumorigenicpotential. Identification of cancer stem cells relies both on 1) theirexpression of a unique pattern of cell-surface receptors used to isolatethem from the bulk of non-tumorigenic tumor cells and 2) theirproperties of self-renewal and proliferation as assessed in xenograftanimal models. This invention relates particularly to the discovery ofsolid tumor stem cells from colon cancer and head and neck cancer.

In one embodiment, the invention provides a method of selecting cells ofa population to obtain a purified population of cancer stem cells (e.g.from a patient biopsy or from human tumor cells passaged via a xenograftin a mouse). The present invention also provides a method of selecting apurified population of tumor cells other than cancer stem cells, such asa population of non-tumorigenic (NTG) tumor cells. Specifically, usingcell-surface markers an ESA+CD44+ tumor cell population from a cancer ofepithelial origin has been identified that is enriched for the abilityto form tumors—is tumorigenic-relative to unfractionated tumor cells andnon-ESA+CD44+ tumor cells (non-tumorigenic cells). The present inventionprovides research methods of characterizing the properties of cancerstem cells from a tumor of epithelial origin. The present inventionprovides methods of raising antibodies to the selected cells. Theinvention provides diagnostic methods using the selected cells. Theinvention also provides therapeutic methods, where the therapeutic isdirected to a cancer stem cell (e.g. directed to one of the cancer stemcell markers identified herein directly or indirectly).

In certain embodiments, the present invention identifies genes that aredifferentially expressed in tumorigenic ESA+44+ colon stem cellscompared to presorted colon tumor cells and to non-ESA+44+ sorted colontumor cells (non-tumorigenic cells) using microarray analysis. A set ofgenes with increased expression in colon cancer stem cells as comparedto non-stem cells is shown in Table 1, and these genes serve as a geneexpression profile of colon cancer stem cells and as colon cancer stemcell markers useful for the characterization, diagnosis, and treatmentof colon cancer stem cells. The differentially expressed genes, and thepeptides encoded thereby, can be detected (e.g. quantitatively) in orderto identify the presence and numbers of solid tumor stem cells, and todetermine and screen molecules suitable for reducing the proliferation,inducing cell death, interfering with self-renewal pathways, orinterfering with survival pathways of any solid tumor stem cells thatare present. The differentially expressed genes, and peptides encodedthereby are also useful for generating therapeutic agents targeted toone or more of these markers (e.g. to inhibit or promote the activity ofthe marker). In certain embodiments of the invention, increasedexpression of HES1 and HES6 in colon cancer stem cells compared tounfractionated colon tumor cells and non-tumorigenic colon tumor cellsis identified in contrast to the Notch target genes HES2, 4 and 7, and acolon cancer stem cell gene marker comprises upregulation of the Notchsignaling pathway target genes HES1 and/or HES6.

In certain embodiments the cancer stem cell markers of the presentinvention can be detected (e.g. in a tumor sample) by expression levelsof polynucleotides by, for example, in situ hybridization or RT-PCR.Furthermore, expression levels of polynucleotides such as, for example,mRNA can be quantified using, for example, Taqman analysis.Alternatively the colon cancer stem cell markers of the presentinvention can be detected in a tumor sample by expression levels ofprotein by, for example, immunohistochemistry or ELISA. Furthermore,protein expression levels can be quantified using, for example,quantitative immunofluorescence. In some embodiments, mRNA expression ofthe colon cancer stem cell marker HES6 is detected (e.g. in a tumorsample) by in situ hybridization. In some embodiments, proteinexpression of the colon cancer stem cell marker HES6 is detected (e.g.in a patient sample) by immunofluorescence using an antibody thatspecifically recognizes HES6. In other embodiments, HES6 expression isdetected in a sample by real-time PCR using primer sets thatspecifically amplify polynucleotides encoding HES6. In other someembodiments, HES6 expression is quantified to determine the number ofcancer stem cells present in a sample (e.g. from a patient).

Accordingly, the invention provides methods of selecting cells,diagnosing disease, conducting research studies, and treating solidtumors using selection methods, diagnostic methods and therapeuticsdirected to specific genes or a given pathway. Included are one or moreof the following genes and gene products: PTGFRN, CD166, CD164, CD82,TGFBR1, MET, EFNB2, ITGA6, TDGF1, HBEGF, ABCC4, ABCD3, TDE2, ITGB1,TNFRSF21, CD81, CD9, KIAA1324, CEACAM6, FZD6, FZD7, BMPR1A, JAG1, ITGAV,NOTCH2, SOX4, HES1, HES6, ATOH1, CDH1, EPHB2, MYB, MYC, SOX9 or STRAP,or lower levels of one or more of TCF4 or VIM, as shown in Table 1 whichare differentially expressed in colon cancer stem cells as compared withnon-tumorigenic cancer cells, as shown herein.

The invention thus provides a method for selectively targetingdiagnostic or therapeutic agents to cancer stem cells. The inventionalso provides an agent, such as a biomolecule, that is selectivelytargeted to cancer stem cells (e.g. directed to one of the colon cancerstem cell cancer markers disclosed herein). In some embodiments, thestem cell cancer marker targeted is part of a self-renewal or cellsurvival pathway. In certain embodiments, the present invention providesmethods for screening for anti-cancer agents; for the testing ofanti-cancer therapies; for the development of drugs targeting novelpathways; for the identification of new anti-cancer therapeutic targets;the identification and diagnosis of malignant cells in pathologyspecimens; for the testing and assaying of solid tumor stem cell drugsensitivity; for the measurement of specific factors that predict drugsensitivity; and for the screening of patients (e.g., as an adjunct formammography).

Other features, objects, and advantages of the invention will beapparent from the detailed description below. Additional guidance isprovided in Published PCT patent application WO 02/12447 by the Regentsof the University of Michigan and PCT patent application PCT/US02/39191by the Regents of the University of Michigan, both of which areincorporated herein by reference.

To facilitate an understanding of the present invention, a number ofterms and phrases are defined below:

An “antibody” is an immunoglobulin molecule that recognizes andspecifically binds to a target, such as a protein, polypeptide, peptide,carbohydrate, polynucleotide, lipid, etc., through at least one antigenrecognition site within the variable region of the immunoglobulinmolecule. As used herein, the term is used in the broadest sense andencompasses intact polyclonal antibodies, intact monoclonal antibodies,antibody fragments (such as Fab, Fab′, F(ab′)₂, and Fv fragments),single chain Fv (scFv) mutants, multispecific antibodies such asbispecific antibodies generated from at least two intact antibodies,fusion proteins comprising an antibody portion, and any other modifiedimmunoglobulin molecule comprising an antigen recognition site so longas the antibodies exhibit the desired biological activity. An antibodycan be of any the five major classes of immunoglobulins: IgA, IgD, IgE,IgG, and IgM, or subclasses (isotypes) thereof (e.g. IgG1, IgG2, IgG3,IgG4, IgA1 and IgA2), based on the identity of their heavy-chainconstant domains referred to as alpha, delta, epsilon, gamma, and mu,respectively. The different classes of immunoglobulins have differentand well known subunit structures and three-dimensional configurations.Antibodies can be naked or conjugated to other molecules such as toxins,radioisotopes, etc.

As used herein, the term “antibody fragments” refers to a portion of anintact antibody. Examples of antibody fragments include, but are notlimited to, linear antibodies; single-chain antibody molecules; Fc orFc′ peptides, Fab and Fab fragments, and multispecific antibodies formedfrom antibody fragments.

As used herein, “humanized” forms of non-human (e.g., murine) antibodiesare chimeric antibodies that contain minimal sequence, or no sequence,derived from non-human immunoglobulin. For the most part, humanizedantibodies are human immunoglobulins (recipient antibody) in whichresidues from a hypervariable region of the recipient are replaced byresidues from a hypervariable region of a non-human species (donorantibody) such as mouse, rat, rabbit or nonhuman primate having thedesired specificity, affinity, and capacity. In some instances, Fvframework region (FR) residues of the human immunoglobulin are replacedby corresponding non-human residues. Furthermore, humanized antibodiescan comprise residues that are not found in the recipient antibody or inthe donor antibody. These modifications are generally made to furtherrefine antibody performance. In general, the humanized antibody willcomprise substantially all of at least one, and typically two, variabledomains, in which all or substantially all of the hypervariable loopscorrespond to those of a nonhuman immunoglobulin and all orsubstantially all of the FR residues are those of a human immunoglobulinsequence. The humanized antibody can also comprise at least a portion ofan immunoglobulin constant region (Fc), typically that of a humanimmunoglobulin. Examples of methods used to generate humanizedantibodies are described in U.S. Pat. No. 5,225,539 to Winter et al.(herein incorporated by reference).

The term “human antibody” as used herein means an antibody produced by ahuman or an antibody having an amino acid sequence corresponding to anantibody produced by a human made using any of the techniques known inthe art. This definition of a human antibody includes intact orfull-length antibodies, fragments thereof, and/or antibodies comprisingat least one human heavy and/or light chain polypeptide such as, forexample, an antibody comprising murine light chain and human heavy chainpolypeptides.

“Hybrid antibodies” are immunoglobulin molecules in which pairs of heavyand light chains from antibodies with different antigenic determinantregions are assembled together so that two different epitopes or twodifferent antigens can be recognized and bound by the resultingtetramer.

The term “chimeric antibodies” refers to antibodies wherein the aminoacid sequence of the immunoglobulin molecule is derived from two or morespecies. Typically, the variable region of both light and heavy chainscorresponds to the variable region of antibodies derived from onespecies of mammals (e.g. mouse, rat, rabbit, etc) with the desiredspecificity, affinity, and capability while the constant regions arehomologous to the sequences in antibodies derived from another (usuallyhuman) to avoid eliciting an immune response in that species.

The term “epitope” or “antigenic determinant” are used interchangeablyherein and refer to that portion of an antigen capable of beingrecognized and specifically bound by a particular antibody. When theantigen is a polypeptide, epitopes can be formed both from contiguousamino acids and noncontiguous amino acids juxtaposed by tertiary foldingof a protein. Epitopes formed from contiguous amino acids are typicallyretained upon protein denaturing, whereas epitopes formed by tertiaryfolding are typically lost upon protein denaturing. An epitope typicallyincludes at least 3, and more usually, at least 5 or 8-10 amino acids ina unique spatial conformation. An antigenic determinant can compete withthe intact antigen (i.e., the “immunogen” used to elicit the immuneresponse) for binding to an antibody.

That an antibody “specifically binds” to or shows “specific binding”towards an epitope means that the antibody reacts or associates morefrequently, more rapidly, with greater duration, and/or with greateraffinity with the epitope than with alternative substances. As usedherein, “specifically binds” means that an antibody binds to a proteinwith a K_(D) of at least about 0.1 mM, at least about 1 uM, at leastabout 0.1 uM or better, or 0.01 uM or better.

As used herein, the terms “non-specific binding” and “backgroundbinding” when used in reference to the interaction of an antibody and aprotein or peptide refer to an interaction that is not dependent on thepresence of a particular structure (i.e., the antibody is binding toproteins in general rather that a particular structure such as anepitope).

As used herein, the term “receptor binding domain” refers to any nativeligand for a receptor, including cell adhesion molecules, or any regionor derivative of such native ligand retaining at least a qualitativereceptor binding ability of a corresponding native ligand.

As used herein, the term “antibody-immunoadhesin chimera” comprises amolecule that combines at least one binding domain of an antibody withat least one immunoadhesin. Examples include, but are not limited to,the bispecific CD4-IgG chimeras described in Berg et al., PNAS (USA)88:4723-4727 (1991) and Charnow et al., J. Immunol., 153:4268 (1994),both of which are hereby incorporated by reference.

“Enriched”, as in an enriched population of cells, can be definedphenotypically based upon the increased number of cells having aparticular marker (e.g. as shown in Table 1) in a fractionated set ofcells as compared with the number of cells having the marker in theunfractionated set of cells. However, the term “enriched” can be definedfunctionally by tumorigenic function as the minimum number of cells thatform tumors at limit dilution frequency in test mice. For example, if500 tumor stem cells form tumors in 63% of test animals, but 5000unfractionated tumor cells are required to form tumors in 63% of testanimals, then the solid tumor stem cell population is 10-fold enrichedfor tumorigenic activity. The stem cell cancer markers of the presentinvention can be used to generate enriched populations of cancer stemcells. In some embodiments, the stem cell population is enriched atleast 1.4 fold relative to unfractionated tumor cells. In otherembodiments, the stem cell population is enriched 2 fold to 10 foldrelative to unfractionated tumor cells. In further embodiments, the stemcell population is enriched 20 fold relative to unfractionated tumorcells.

“Isolated” in regard to cells, refers to a cell that is removed from itsnatural environment (such as in a solid tumor) and that is isolated orseparated, and is at least about 30%, 50%, 75% free, or about 90% free,from other cells with which it is naturally present, but which lack themarker based on which the cells were isolated. The stem cell cancermarkers of the present invention can be used to generate isolatedpopulations of cancer stem cells.

As used herein, the terms “cancer” and “cancerous” refer to or describethe physiological condition in mammals in which a population of cellsare characterized by unregulated cell growth. Examples of cancerinclude, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma,and leukemia. More particular examples of such cancers include squamouscell cancer, small-cell lung cancer, non-small cell lung cancer,adenocarcinoma of the lung, squamous carcinoma of the lung, cancer ofthe peritoneum, hepatocellular cancer, gastrointestinal cancer,pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, livercancer, bladder cancer, hepatoma, breast cancer, colon cancer,colorectal cancer, endometrial or uterine carcinoma, salivary glandcarcinoma, kidney cancer, liver cancer, prostate cancer, vulval cancer,thyroid cancer, hepatic carcinoma and various types of head and neckcancer.

“Metastasis” as used herein refers to the process by which a cancerspreads or transfers from the site of origin to other regions of thebody with the development of a similar cancerous lesion at the newlocation. A “metastatic” or “metastasizing” cell is one that losesadhesive contacts with neighboring cells and migrates via thebloodstream or lymph from the primary site of disease to invadeneighboring body structures.

As used herein, the term “subject” refers to any animal (e.g., amammal), including, but not limited to, humans, non-human primates,rodents, and the like, which is to be the recipient of a particulartreatment. Typically, the terms “subject” and “patient” are usedinterchangeably herein in reference to a human subject.

As used herein, the term “subject suspected of having cancer” refers toa subject that presents one or more symptoms indicative of a cancer(e.g., a noticeable lump or mass) or is being screened for a cancer(e.g., during a routine physical). A subject suspected of having cancercan also have one or more risk factors. A subject suspected of havingcancer has generally not been tested for cancer. However, a “subjectsuspected of having cancer” encompasses an individual who has receivedan initial diagnosis but for whom the stage of cancer is not known. Theterm further includes people who once had cancer (e.g., an individual inremission).

As used herein, the term “subject at risk for cancer” refers to asubject with one or more risk factors for developing a specific cancer.Risk factors include, but are not limited to, gender, age, geneticpredisposition, environmental exposure, previous incidents of cancer,preexisting non-cancer diseases, and lifestyle.

As used herein, the term “characterizing cancer in a subject” refers tothe identification of one or more properties of a cancer sample in asubject, including but not limited to, the presence of benign,pre-cancerous or cancerous tissue, the stage of the cancer, and thesubject's prognosis. Cancers can be characterized by the identificationof the expression of one or more cancer marker genes, including but notlimited to, the cancer markers disclosed herein.

The terms “cancer stem cell”, “tumor stem cell”, or “solid tumor stemcell” are used interchangeably herein and refer to a population of cellsfrom a solid tumor that: (1) have extensive proliferative capacity; (2)are capable of asymmetric cell division to generate one or more kinds ofdifferentiated progeny with reduced proliferative or developmentalpotential; and (3) are capable of symmetric cell divisions forself-renewal or self-maintenance. These properties of “cancer stemcells”, “tumor stem cells” or “solid tumor stem cells” confer on thosecancer stem cells the ability to form palpable tumors upon serialtransplantation into an immunocompromised mouse compared to the majorityof tumor cells that fail to generate tumors. Cancer stem cells undergoself-renewal versus differentiation in a chaotic manner to form tumorswith abnormal cell types that can change over time as mutations occur.The solid tumor stem cells of the present invention differ from the“cancer stem line” provided by U.S. Pat. No. 6,004,528. In that patent,the “cancer stem line” is defined as a slow growing progenitor cell typethat itself has few mutations but which undergoes symmetric rather thanasymmetric cell divisions as a result of tumorigenic changes that occurin the cell's environment. This “cancer stem line” hypothesis thusproposes that highly mutated, rapidly proliferating tumor cells ariselargely as a result of an abnormal environment, which causes relativelynormal stem cells to accumulate and then undergo mutations that causethem to become tumor cells. U.S. Pat. No. 6,004,528 proposes that such amodel can be used to enhance the diagnosis of cancer. The solid tumorstem cell model is fundamentally different than the “cancer stem line”model and as a result exhibits utilities not offered by the “cancer stemline” model. First, solid tumor stem cells are not “mutationallyspared”. The “mutationally spared cancer stem line” described by U.S.Pat. No. 6,004,528 can be considered a pre-cancerous lesion, while thesolid tumor stem cells described by this invention are cancer cells thatthemselves contain the mutations that are responsible for tumorigenesis.That is, the solid tumor stem cells (“cancer stem cells”) of theinvention would be included among the highly mutated cells that aredistinguished from the “cancer stem line” in U.S. Pat. No. 6,004,528.Second, the genetic mutations that lead to cancer can be largelyintrinsic within the solid tumor stem cells as well as beingenvironmental. The solid tumor stem cell model predicts that isolatedsolid tumor stem cells can give rise to additional tumors upontransplantation (thus explaining metastasis) while the “cancer stemline” model would predict that transplanted “cancer stem line” cellswould not be able to give rise to a new tumor, since it was theirabnormal environment that was tumorigenic. Indeed, the ability totransplant dissociated, and phenotypically isolated human solid tumorstem cells to mice (into an environment that is very different from thenormal tumor environment), where they still form new tumors,distinguishes the present invention from the “cancer stem line” model.Third, solid tumor stem cells likely divide both symmetrically andasymmetrically, such that symmetric cell division is not an obligateproperty. Fourth, solid tumor stem cells can divide rapidly or slowly,depending on many variables, such that a slow proliferation rate is nota defining characteristic.

As used herein “tumorigenic” refers to the functional features of asolid tumor stem cell including the properties of self-renewal (givingrise to additional tumorigenic cancer stem cells) and proliferation togenerate all other tumor cells (giving rise to differentiated and thusnon-tumorigenic tumor cells) that allow solid tumor stem cells to form atumor. These properties of self-renewal and proliferation to generateall other tumor cells confer on the cancer stem cells of this inventionthe ability to form palpable tumors upon serial transplantation into animmunocompromised mouse compared to the majority of tumor cells that areunable to form tumors upon the serial transplantation. Tumor cells, i.e.non-tumorigenic tumor cells, may form a tumor upon transplantation intoan immunocompromised mouse a limited number of times (for example one ortwo times) after obtaining the tumor cells from a solid tumor.

As used herein, the terms “stem cell cancer marker(s)”, “cancer stemcell marker(s)”, “tumor stem cell marker(s)”, or “solid tumor stem cellmarker(s)” refer to a gene or genes or a protein, polypeptide, orpeptide expressed by the gene or genes whose expression level, alone orin combination with other genes, is correlated with the presence oftumorigenic cancer cells compared to non-tumorigenic cells. Thecorrelation can relate to either an increased or decreased expression ofthe gene (e.g. increased or decreased levels of mRNA or the peptideencoded by the gene).

As used herein, the terms “unfractionated tumor cells”, “presorted tumorcells”, “bulk tumor cells”, and their grammatical equivalents are usedinterchangeably to refer to a tumor cell population isolated from apatient sample (e.g. a tumor biopsy or pleural effusion) that has notbeen segregated, or fractionated, based on cell surface markerexpression.

As used herein, the terms “non-ESA+CD44+ tumor cells”, “non-ESA+44+”,“sorted non-tumorigenic tumor cells”, “non-tumorigenic tumor cells,”“non-stem cells,” “tumor cells” and their grammatical equivalents areused interchangeably to refer to a tumor population from which thecancer stem cells of this invention have been segregated, or removed,based on cell surface marker expression.

“Gene expression profile” refers to identified expression levels of atleast one polynucleotide or protein expressed in a biological sample.

A “gene profile,” “gene pattern,” “expression pattern” or “expressionprofile” refers to a specific pattern of gene expression that provides aunique identifier of a biological sample, for example, a breast or coloncancer pattern of gene expression, obtained by analyzing a breast orcolon cancer sample and in those cases can be referred to as a “breastcancer gene profile” or a “colon cancer expression pattern”. “Genepatterns” can be used to diagnose a disease, make a prognosis, select atherapy, and/or monitor a disease or therapy after comparing the genepattern to a cancer stem cell gene signature.

As used herein, the term “gene expression” refers to the process ofconverting genetic information encoded in a gene into RNA (e.g., mRNA,rRNA, tRNA, or snRNA) through “transcription” of the gene (e.g., via theenzymatic action of an RNA polymerase), and for protein encoding genes,into protein through “translation” of mRNA. Gene expression can beregulated at many stages in the process. “Up-regulation” or “activation”refers to regulation that increases the production of gene expressionproducts (e.g., RNA or protein), while “down-regulation” or “repression”refers to regulation that decrease production. Molecules (e.g.,transcription factors) that are involved in up-regulation ordown-regulation are often called “activators” and “repressors,”respectively.

The terms “high levels”, “increased levels”, “high expression”,“increased expression”, “elevated levels” or “upregulated expression” inregards to gene expression are used herein interchangeably to refer toexpression of a gene in a cell or population of cells, particularly acancer stem cell or population of cancer stem cells, at levels higherthan the expression of that gene in a second cell or population ofcells, for example, unfractionated colon tumor cells or non-ESA+44+colon tumor cells. “Elevated levels” of gene expression refers toexpression of a gene in a cancer stem cell or population of cancer stemcells at levels twice that or more of expression levels of the same genein unfractionated colon tumor cells or non-ESA+44+ colon tumor cells.“Elevated levels” of gene expression also refers to expression of a genein a cancer stem cell or population of cancer stem cells at levels sixtimes that or more of expression levels of the same gene inunfractionated colon tumor cells or non-ESA+44+ colon tumor cells.“Elevated levels” of gene expression can be determined by detectingincreased amounts of a polynucleotide (mRNA, cDNA, etc.) in cancer stemcells compared to unfractionated colon tumor cells or non-ESA+44+ colontumor cells by, for example, quantitative RT-PCR or microarray analysis.Alternatively “elevated levels” of gene expression can be determined bydetecting increased amounts of a protein in cancer stem cells comparedto unfractionated colon tumor cells or non-ESA+44+ colon tumor cells by,for example, ELISA, Western blot, quantitative immunfluorescence.

The term “undetectable levels” or “loss of expression” in regards togene expression as used herein refers to expression of a gene in a cellor population of cells, particularly a cancer stem cell or population ofcancer stem cells, at levels that cannot be distinguished frombackground using conventional techniques such that no expression isidentified. “Undetectable levels” of gene expression can be determinedby the inability to detect levels of a polynucleotide (mRNA, cDNA, etc.)in cancer stem cells above background by, for example, quantitativeRT-PCR or microarray analysis. Alternatively “undetectable levels” ofgene expression can be determined by the inability to detect levels of aprotein in cancer stem cells above background by, for example, ELISA,Western blot, or immunofluorescence.

As used herein, the terms “low levels”, “decreased levels”, “lowexpression”, “reduced expression” or “decreased expression” in regardsto gene expression are used herein interchangeably to refer toexpression of a gene in a cell or population of cells, particularly acancer stem cell or population of cancer stem cells, at levels less thanthe expression of that gene in a second cell or population of cells, forexample unfractionated colon tumor cells or non-ESA+44+ colon tumorcells. “Low levels” of gene expression refers to expression of a gene ina cancer stem cell or population of cancer stem cells at levels: 1) halfthat or below expression levels of the same gene in unfractionated colontumor cells or non-ESA+44+ colon tumor cells and 2) at the lower limitof detection using conventional techniques. “Low levels” of geneexpression can be determined by detecting decreased to nearlyundetectable amounts of a polynucleotide (mRNA, cDNA, etc.) in cancerstem cells compared to unfractionated colon tumor cells or non-ESA+44+colon tumor cells by, for example, quantitative RT-PCR or microarrayanalysis. Alternatively “low levels” of gene expression can bedetermined by detecting decreased to nearly undetectable amounts of aprotein in cancer stem cells compared to unfractionated colon tumorcells or non-ESA+44+ colon tumor cells by, for example, ELISA, Westernblot, or quantitative immunfluorescence.

As used herein, the term “a reagent that specifically detects expressionlevels” refers to reagents used to detect the expression of one or moregenes (e.g., including but not limited to, the cancer markers of thepresent invention). Examples of suitable reagents include but are notlimited to, nucleic acid probes capable of specifically hybridizing tothe gene of interest, aptamers, PCR primers capable of specificallyamplifying the gene of interest, and antibodies capable of specificallybinding to proteins expressed by the gene of interest. Othernon-limiting examples can be found in the description and examplesbelow.

As used herein, the term “detecting a decreased or increased expressionrelative to non-cancerous control” refers to measuring the level ofexpression of a gene (e.g., the level of mRNA or protein) relative tothe level in a non-cancerous control sample. Gene expression can bemeasured using any suitable method, including but not limited to, thosedescribed herein.

As used herein, the term “detecting a change in gene expression in acell sample in the presence of said test compound relative to theabsence of said test compound” refers to measuring an altered level ofexpression (e.g., increased or decreased) in the presence of a testcompound relative to the absence of the test compound. Gene expressioncan be measured using any suitable method.

As used herein, the term “instructions for using said kit for detectingcancer in said subject” includes instructions for using the reagentscontained in the kit for the detection and characterization of cancer ina sample from a subject.

As used herein, “providing a diagnosis” or “diagnostic information”refers to any information that is useful in determining whether apatient has a disease or condition and/or in classifying the disease orcondition into a phenotypic category or any category having significancewith regards to the prognosis of or likely response to treatment (eithertreatment in general or any particular treatment) of the disease orcondition. Similarly, diagnosis refers to providing any type ofdiagnostic information, including, but not limited to, whether a subjectis likely to have a condition (such as a tumor), information related tothe nature or classification of a tumor as for example a high risk tumoror a low risk tumor, information related to prognosis and/or informationuseful in selecting an appropriate treatment. Selection of treatment caninclude the choice of a particular chemotherapeutic agent or othertreatment modality such as surgery or radiation or a choice aboutwhether to withhold or deliver therapy.

As used herein, the terms “providing a prognosis”, “prognosticinformation”, or “predictive information” refer to providing informationregarding the impact of the presence of cancer (e.g., as determined bythe diagnostic methods of the present invention) on a subject's futurehealth (e.g., expected morbidity or mortality, the likelihood of gettingcancer, and the risk of metastasis).

As used herein, the term “post surgical tumor tissue” refers tocancerous tissue (e.g., biopsy tissue) that has been removed from asubject (e.g., during surgery).

As used herein, the term “subject diagnosed with a cancer” refers to asubject who has been tested and found to have cancerous cells. Thecancer can be diagnosed using any suitable method, including but notlimited to, biopsy, x-ray, blood test, and the diagnostic methods of thepresent invention.

As used herein, the terms “biopsy tissue”, “patient sample”, “tumorsample”, and “cancer sample” refer to a sample of cells, tissue or fluidthat is removed from a subject for the purpose of determining if thesample contains cancerous tissue, including cancer stem cells or fordetermining gene expression profile of that cancerous tissue. In someembodiment, biopsy tissue or fluid is obtained because a subject issuspected of having cancer. The biopsy tissue or fluid is then examinedfor the presence or absence of cancer, cancer stem cells, and/or cancerstem cell gene signature expression.

As used herein, the term “gene transfer system” refers to any means ofdelivering a composition comprising a nucleic acid sequence to a cell ortissue. For example, gene transfer systems include, but are not limitedto, vectors (e.g., retroviral, adenoviral, adeno-associated viral, andother nucleic acid-based delivery systems), microinjection of nakednucleic acid, polymer-based delivery systems (e.g., liposome-based andmetallic particle-based systems), biolistic injection, and the like. Asused herein, the term “viral gene transfer system” refers to genetransfer systems comprising viral elements (e.g., intact viruses,modified viruses and viral components such as nucleic acids or proteins)to facilitate delivery of the sample to a desired cell or tissue. Asused herein, the term “adenovirus gene transfer system” refers to genetransfer systems comprising intact or altered viruses belonging to thefamily Adenoviridae.

As used herein, the term “site-specific recombination target sequences”refers to nucleic acid sequences that provide recognition sequences forrecombination factors and the location where recombination takes place.

As used herein, the term “nucleic acid molecule” refers to any nucleicacid containing molecule, including but not limited to, DNA or RNA. Theterm encompasses sequences that include any of the known base analogs ofDNA and RNA including, but not limited to, 4-acetylcytosine,8-hydroxy-N6-methyladenosine, aziridinylcytosine, pseudoisocytosine,5-(carboxyhydroxylmethyl) uracil, 5-fluorouracil, 5-bromouracil,5-carboxymethylaminomethyl-2-thiouracil,5-carboxymethylaminomethyluracil, dihydrouracil, inosine,N6-isopentenyladenine, 1-methyladenine, 1-methylpseudouracil,1-methylguanine, 1-methylinosine, 2,2-dimethylguanine, 2-methyladenine,2-methylguanine, 3-methylcytosine, 5-methylcytosine, N6-methyladenine,7-methylguanine, 5-methylaminomethyluracil,5-methoxyaminomethyl-2-thiouracil, beta-D-mannosylqueosine,5′-methoxycarbonylmethyluracil, 5-methoxyuracil,2-methylthio-N6-isopentenyladenine, uracil-5-oxyacetic acid methylester,uracil-5-oxyacetic acid, oxybutoxosine, pseudouracil, queosine,2-thiocytosine, 5-methyl-2-thiouracil, 2-thiouracil, 4-thiouracil,5-methyluracil, N-uracil-5-oxyacetic acid methylester,uracil-5-oxyacetic acid, pseudouracil, queosine, 2-thiocytosine, and2,6-diaminopurine.

The term “gene” refers to a nucleic acid (e.g., DNA) sequence thatcomprises coding sequences necessary for the production of apolypeptide, precursor, or RNA (e.g., rRNA, tRNA). The polypeptide canbe encoded by a full length coding sequence or by any portion of thecoding sequence so long as the desired activity or functional properties(e.g., enzymatic activity, ligand binding, signal transduction,immunogenicity, etc.) of the full-length or fragment are retained. Theterm also encompasses the coding region of a structural gene and thesequences located adjacent to the coding region on both the 5′ and 3′ends for a distance of about 1 kb or more on either end such that thegene corresponds to the length of the full-length mRNA. Sequenceslocated 5′ of the coding region and present on the mRNA are referred toas 5′ non-translated sequences. Sequences located 3′ or downstream ofthe coding region and present on the mRNA are referred to as 3′non-translated sequences. The term “gene” encompasses both cDNA andgenomic forms of a gene. A genomic form or clone of a gene contains thecoding region interrupted with non-coding sequences termed “introns” or“intervening regions” or “intervening sequences.” Introns are segmentsof a gene that are transcribed into nuclear RNA (hnRNA); introns cancontain regulatory elements such as enhancers. Introns are removed or“spliced out” from the nuclear or primary transcript; introns thereforeare absent in the messenger RNA (mRNA) transcript. The mRNA functionsduring translation to specify the sequence or order of amino acids in anascent polypeptide.

As used herein, the term “heterologous gene” refers to a gene that isnot in its natural environment. For example, a heterologous geneincludes a gene from one species introduced into another species. Aheterologous gene also includes a gene native to an organism that hasbeen altered in some way (e.g., mutated, added in multiple copies,linked to non-native regulatory sequences, etc). Heterologous genes aredistinguished from endogenous genes in that the heterologous genesequences are typically joined to DNA sequences that are not foundnaturally associated with the gene sequences in the chromosome or areassociated with portions of the chromosome not found in nature (e.g.,genes expressed in loci where the gene is not normally expressed).

As used herein, the term “gene expression” refers to the process ofconverting genetic information encoded in a gene into RNA (e.g., mRNA,rRNA, tRNA, or snRNA) through “transcription” of the gene (e.g., via theenzymatic action of an RNA polymerase), and for protein encoding genes,into protein through “translation” of mRNA. Gene expression can beregulated at many stages in the process. “Up-regulation” or “activation”refers to regulation that increases the production of gene expressionproducts (e.g., RNA or protein), while “down-regulation” or “repression”refers to regulation that decrease production. Molecules (e.g.,transcription factors) that are involved in up-regulation ordown-regulation are often called “activators” and “repressors,”respectively.

In addition to containing introns, genomic forms of a gene can alsoinclude sequences located on both the 5′ and 3′ end of the sequencesthat are present on the RNA transcript. These sequences are referred toas “flanking” sequences or regions (these flanking sequences are located5′ or 3′ to the non-translated sequences present on the mRNAtranscript). The 5′ flanking region can contain regulatory sequencessuch as promoters and enhancers that control or influence thetranscription of the gene. The 3′ flanking region can contain sequencesthat direct the termination of transcription, post-transcriptionalcleavage and polyadenylation.

The term “siRNAs” refers to short interfering RNAs. In some embodiments,siRNAs comprise a duplex, or double-stranded region, of about 18-25nucleotides long; often siRNAs contain from about two to four unpairednucleotides at the 3′ end of each strand. At least one strand of theduplex or double-stranded region of a siRNA is substantially homologousto or substantially complementary to a target RNA molecule. The strandcomplementary to a target RNA molecule is the “antisense strand;” thestrand homologous to the target RNA molecule is the “sense strand,” andis also complementary to the siRNA antisense strand. siRNAs can alsocontain additional sequences; non-limiting examples of such sequencesinclude linking sequences, or loops, as well as stem and other foldedstructures. siRNAs appear to function as key intermediaries intriggering RNA interference in invertebrates and in vertebrates, and intriggering sequence-specific RNA degradation during posttranscriptionalgene silencing in plants.

The term “RNA interference” or “RNAi” refers to the silencing ordecreasing of gene expression by siRNAs. It is the process ofsequence-specific, post-transcriptional gene silencing in animals andplants, initiated by siRNA that is homologous in its duplex region tothe sequence of the silenced gene. The gene can be endogenous orexogenous to the organism, present integrated into a chromosome orpresent in a transfection vector that is not integrated into the genome.The expression of the gene is either completely or partially inhibited.RNAi can also be considered to inhibit the function of a target RNA; thefunction of the target RNA can be complete or partial.

As used herein, the terms “nucleic acid molecule encoding,” “DNAsequence encoding,” and “DNA encoding” refer to the order or sequence ofdeoxyribonucleotides along a strand of deoxyribonucleic acid. The orderof these deoxyribonucleotides determines the order of amino acids alongthe polypeptide (protein) chain. The DNA sequence thus codes for theamino acid sequence.

As used herein, the terms “an oligonucleotide having a nucleotidesequence encoding a gene” and “polynucleotide having a nucleotidesequence encoding a gene,” means a nucleic acid sequence comprising thecoding region of a gene or in other words the nucleic acid sequence thatencodes a gene product. The coding region can be present in a cDNA,genomic DNA or RNA form. When present in a DNA form, the oligonucleotideor polynucleotide can be single-stranded (i.e., the sense strand) ordouble-stranded. Suitable control elements such as enhancers/promoters,splice junctions, polyadenylation signals, etc. can be placed in closeproximity to the coding region of the gene if needed to permit properinitiation of transcription and/or correct processing of the primary RNAtranscript. Alternatively, the coding region utilized in the expressionvectors of the present invention can contain endogenousenhancers/promoters, splice junctions, intervening sequences,polyadenylation signals, etc. or a combination of both endogenous andexogenous control elements.

As used herein the term “portion” when in reference to a nucleotidesequence (as in “a portion of a given nucleotide sequence”) refers tofragments of that sequence. The fragments can range in size from fournucleotides to the entire nucleotide sequence minus one nucleotide (10nucleotides, 20, 30, 40, 50, 100, 200, etc.).

The phrases “hybridizes”, “selectively hybridizes”, or “specificallyhybridizes” refer to the binding or duplexing of a molecule only to aparticular nucleotide sequence under stringent hybridization conditionswhen that sequence is present in a complex mixture (e.g., a library ofDNAs or RNAs). See, e.g., Andersen (1998) Nucleic Acid HybridizationSpringer-Verlag; Ross (ed. 1997) Nucleic Acid Hybridization Wiley.

The phrase “stringent hybridization conditions” refers to conditionsunder which a probe will hybridize to its target subsequence, typicallyin a complex mixture of nucleic acid, but to no other sequences.Stringent conditions are sequence-dependent and will be different indifferent circumstances. Longer sequences hybridize specifically athigher temperatures. An extensive guide to the hybridization of nucleicacids is found in Tijssen, Techniques in Biochemistry and MolecularBiology—Hybridization with Nucleic Probes, “Overview of principles ofhybridization and the strategy of nucleic acid assays” (1993).Generally, stringent conditions are selected to be about 5-10° C. lowerthan the thermal melting point (Tm) for the specific sequence at adefined ionic strength. The Tm is the temperature (under defined ionicstrength, pH, and nucleic concentration) at which 50% of the probescomplementary to the target hybridize to the target sequence atequilibrium (as the target sequences are present in excess, at Tm, 50%of the probes are occupied at equilibrium). Stringent conditions will bethose in which the salt concentration is less than about 1.0 M sodiumion, typically about 0.01 to 1.0 M sodium ion concentration (or othersalts) at pH 7.0 to 8.3 and the temperature is at least about 30° C. forshort probes (e.g., 10 to 50 nucleotides) and at least about 60° C. forlong probes (e.g., greater than 50 nucleotides). Stringent conditionscan also be achieved with the addition of destabilizing agents such asformamide. For high stringency hybridization, a positive signal is atleast two times background, or 10 times background hybridization.Exemplary high stringency or stringent hybridization conditions include:50% formamide, 5×SSC, and 1% SDS incubated at 42° C. or 5×SSC and 1% SDSincubated at 65° C., with a wash in 0.2×SSC and 0.1% SDS at 65° C. ForPCR, a temperature of about 36° C. is typical for low stringencyamplification, although annealing temperatures can vary from about 32°C. to about 48° C. depending on primer length. For high stringency PCRamplification, a temperature of about 62° C. is typical, although highstringency annealing temperatures can range from about 50° C. to about65° C., depending on the primer length and specificity. Typical cycleconditions for both high and low stringency amplifications include adenaturation phase of 90° C. to 95° C. for 30-120 sec, an annealingphase lasting 30-120 sec, and an extension phase of about 72° C. for 1-2min.

The terms “in operable combination,” “in operable order,” and “operablylinked” as used herein refer to the linkage of nucleic acid sequences insuch a manner that a nucleic acid molecule capable of directing thetranscription of a given gene and/or the synthesis of a desired proteinmolecule is produced. The term also refers to the linkage of amino acidsequences in such a manner so that a functional protein is produced.

The term “isolated” when used in relation to a nucleic acid, as in “anisolated oligonucleotide” or “isolated polynucleotide” refers to anucleic acid sequence that is identified and separated from at least onecomponent or contaminant with which it is ordinarily associated in itsnatural source. Isolated nucleic acid is such present in a form orsetting that is different from that in which it is found in nature. Incontrast, non-isolated nucleic acids as nucleic acids such as DNA andRNA found in the state they exist in nature. For example, a given DNAsequence (e.g., a gene) is found on the host cell chromosome inproximity to neighboring genes; RNA sequences, such as a specific mRNAsequence encoding a specific protein, are found in the cell as a mixturewith numerous other mRNAs that encode a multitude of proteins. However,isolated nucleic acid encoding a given protein includes, by way ofexample, such nucleic acid in cells ordinarily expressing the givenprotein where the nucleic acid is in a chromosomal location differentfrom that of natural cells, or is otherwise flanked by a differentnucleic acid sequence than that found in nature. The isolated nucleicacid, oligonucleotide, or polynucleotide can be present insingle-stranded or double-stranded form. When an isolated nucleic acid,oligonucleotide or polynucleotide is to be utilized to express aprotein, the oligonucleotide or polynucleotide will contain at a minimumthe sense or coding strand (i.e., the oligonucleotide or polynucleotidecan be single-stranded), but can contain both the sense and anti-sensestrands (i.e., the oligonucleotide or polynucleotide can bedouble-stranded).

“Amino acid sequence” and terms such as “polypeptide”, “protein”, or“peptide” are not meant to limit the amino acid sequence to thecomplete, native amino acid sequence associated with the recited proteinmolecule.

The term “native protein” as used herein to indicate that a protein doesnot contain amino acid residues encoded by vector sequences; that is,the native protein contains only those amino acids found in the proteinas it occurs in nature. A native protein can be produced byrecombinantly or can be isolated from a naturally occurring source.

As used herein the term “portion” when in reference to a protein (as in“a portion of a given protein”) refers to fragments of that protein. Thefragments can range in size from four amino acid residues to the entireamino acid sequence minus one amino acid.

The term “Southern blot,” refers to the analysis of DNA on agarose oracrylamide gels to fractionate the DNA according to size followed bytransfer of the DNA from the gel to a solid support, such asnitrocellulose or a nylon membrane. The immobilized DNA is then probedwith a labeled probe to detect DNA species complementary to the probeused. The DNA can be cleaved with restriction enzymes prior toelectrophoresis. Following electrophoresis, the DNA can be partiallydepurinated and denatured prior to or during transfer to the solidsupport. Southern blots are a standard tool of molecular biologists (J.Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold SpringHarbor Press, NY, pp 9.31-9.58 [1989]).

The term “Northern blot,” as used herein refers to the analysis of RNAby electrophoresis of RNA on agarose gels to fractionate the RNAaccording to size followed by transfer of the RNA from the gel to asolid support, such as nitrocellulose or a nylon membrane. Theimmobilized RNA is then probed with a labeled probe to detect RNAspecies complementary to the probe used. Northern blots are a standardtool of molecular biologists (J. Sambrook, et al., supra, pp 7.39-7.52[1989]).

The term “Western blot” refers to the analysis of protein(s) (orpolypeptides) immobilized onto a support such as nitrocellulose or amembrane. The proteins are run on acrylamide gels to separate theproteins, followed by transfer of the protein from the gel to a solidsupport, such as nitrocellulose or a nylon membrane. The immobilizedproteins are then exposed to antibodies with reactivity against anantigen of interest. The binding of the antibodies can be detected byvarious methods, including the use of radiolabeled antibodies.

The term “transgene” as used herein refers to a foreign gene that isplaced into an organism by, for example, introducing the foreign geneinto newly fertilized eggs or early embryos. The term “foreign gene”refers to any nucleic acid (e.g., gene sequence) that is introduced intothe genome of an animal by experimental manipulations and can includegene sequences found in that animal so long as the introduced gene doesnot reside in the same location as does the naturally occurring gene.

As used herein, the term “vector” is used in reference to nucleic acidmolecules that transfer DNA segment(s) from one cell to another. Theterm “vehicle” is sometimes used interchangeably with “vector.” Vectorsare often derived from plasmids, bacteriophages, or plant or animalviruses.

The term “expression vector” as used herein refers to a recombinant DNAmolecule containing a desired coding sequence and appropriate nucleicacid sequences necessary for the expression of the operably linkedcoding sequence in a particular host organism. Nucleic acid sequencesnecessary for expression in prokaryotes usually include a promoter, anoperator (optional), and a ribosome binding site, often along with othersequences. Eukaryotic cells are known to utilize promoters, enhancers,and termination and polyadenylation signals.

As used herein, the term “in vitro” refers to an artificial environmentand to processes or reactions that occur within an artificialenvironment. In vitro environments can consist of, but are not limitedto, test tubes and cell culture. The term “in vivo” refers to thenatural environment (e.g., an animal or a cell) and to processes orreaction that occur within a natural environment.

The terms “test compound” and “candidate compound” refer to any chemicalentity, pharmaceutical, drug, and the like that is a candidate for useto treat or prevent a disease, illness, sickness, or disorder of bodilyfunction (e.g., cancer). Test compounds comprise both known andpotential therapeutic compounds. A test compound can be determined to betherapeutic by screening using the screening methods of the presentinvention. In some embodiments of the present invention, test compoundsinclude antisense compounds.

As used herein, the term “sample” is used in its broadest sense. In onesense, it is meant to include a specimen or culture obtained from anysource, as well as biological and environmental samples. Biologicalsamples can be obtained from animals (including humans) and encompassfluids, solids, tissues, and gases. Biological samples include bloodproducts, such as plasma, serum and the like. Environmental samplesinclude environmental material such as surface matter, soil, water,crystals and industrial samples. Such examples are not however to beconstrued as limiting the sample types applicable to the presentinvention.

By “specific binding” or “unique binding” is intended when an agentbinds only to a particular ligand, receptor, or antigen. By “selectivebinding” is intended when an agent preferably binds to a ligand,receptor, or antigen over others by a magnitude of about two-fold orgreat, about five-fold or greater, about eight-fold or greater, or aboutten-fold or greater.

As used herein, “about” refers to plus or minus 10% of the indicatednumber. For example, “about 10%” indicates a range of 9% to 11%.

The present invention provides compositions and methods for treating,characterizing, and diagnosing cancer. In particular, the presentinvention provides gene expression profiles associated with solid tumorstem cells, as well as novel markers useful for the diagnosis,characterization, and treatment of solid tumor stem cells.

Solid Tumor Stem Cells Cancer Markers

The present invention provides markers whose expression isdifferentially expressed in colon cancer stem cells compared tounfractionated colon tumor cells or non-ESA+44+ colon tumor cells. Suchmarkers find use in the diagnosis and characterization and alteration(e.g., therapeutic targeting) of various cancers (e.g. colon cancer).

Example 1, provided below, describes methods used to identify solidtumor cancer markers. Preferred cancer markers are provided below inTable 1. While these tables provide gene names, it is noted that thepresent invention contemplates the use of both the nucleic acidsequences as well as the peptides encoded thereby, as well as fragmentsof the nucleic acid and peptides, in the therapeutic and diagnosticmethods and compositions of the present invention. TABLE 1 Solid TumorCancer Markers Up, or Down, Regulated in Tumorigenic Colon Cancer StemCells versus Non-Tumorigenic Cancer Cells UPREGULATED PTGFRN CD166 CD164CD82 TGFBR1 MET EFNB2 ITGA6 (CD49f) TDGF1 HBEGF ABCC4 ABCD3 TDE2 ITGB1TNFRSF21 CD81 CD9 KIAA1324 HES6 SOX4 FZD6 FZD7 BMPR1A JAG1 ITGAV NOTCH2ATOH1 CDH1 EPHB2 MYB MYC SOX9 STRAP HES1 CD59 PCGF1, ALDH1A1 4(BMI1), 5DOWNREGULATED TCF4 VIM

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of prostaglandin F2 receptorregulatory protein (PTGFRN or FPRP), CD81 and CD9 compared tonon-tumorigenic colon tumor cells. PTGFRN is a member of thecell-surface Ig superfamily and associates robustly and specificallywith CD81 and CD9, two members of the transmembrane-4 superfamily (TM4SFor tetraspanins) in cancer cell lines (Stipp et al., 2001, J. Biol.Chem. 276:4853-62; Charrin et al., 2001, J. Biol. Chem. 276:14329-37).PTGFRN contains six extracellular immunoglobulin domains and associateswith seven transmembrane receptors including the prostaglandin F_(2α)receptor to reduce receptor ligand binding capacity (Orlicky, 1996,Prostaglandins Leukotrienes Essent. Fatty Acids 54:247-59: Orlicky etal., 1998, J. Lipid Res. 39:1152-61). Tetraspanins have been implicatedin many cellular functions including adhesion, migration, signaltransduction, and differentiation. CD81 knockout mice demonstrate a rolefor CD81 in B cell signaling and activation as well as T-cellproliferation (Maecker & Levy, 1997, J. Exp. Med. 185:1505-10; Tsitsikovet al., 1997, PNAS 94:10844-49; Miyazaki et al., 1997, EMBO J.16:4217-25) whereas CD9 knockout mice show reduced fertilization due toimpaired fusion of sperm and egg (Miyado et al., 2000, Science287:321-4; Le Naour et al., 2000, Science 287:319-21). Furthermore, CD9can act as a suppressor of metastasis as its expression in tumors ininversely correlated with metastases and it can reduce the metastaticpotential of melanoma cells (Ikeyama et al., 1993, J. Exp. Med.177:1231-37; Si & Hersey, 1993, Int. J. Cancer 54:37-43; Miyake et al.,1995, Cancer Res. 55:4127-31; Adachi et al., 1998, J. Clin. Oncol.16:1397-1406; Mori et al., 1998, Clin. Cancer Res. 4:1507-10). Yet, bothCD81 and CD9 lack obvious intracellular signaling domains and can act asadaptors to connect a subset of cell-surface proteins into a network, ortetraspanin web (Maecker et al., 1997, 1997, FASEB J. 11:428-442;Rubinstein et al., 1996, Eur. J. Immunol. 26:2657-65). That PTGFRN, CD81and CD9 have been identified as a discrete biochemical entity and thatall are upregulated in colon cancer stem cells suggests that thiscomplex can play a role in stem cell biology and serve as a usefultarget for cancer therapies.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of CD166 (or activated leukocyteadhesion molecule; ALCAM) compared to non-tumorigenic colon tumor cells.CD166 is a member of the immunoglobulin superfamily with fiveextracellular immunoglobulin-like domains and promotes both heterophilicand homophilic cell-cell interactions. CD166 shows broad expression inepithelia, neurons, lymphoid and myeloid cells, hematopoietic andmesenchymal stem cells and functions in the development and maintenanceof tissue architecture, neurogenesis, hematopoiesis, immune responsesand tumor progression (Swart, 2002, Eur. J. Cell Biol. 81:313-21). CD166expression generally occurs in proliferating cells including a number ofcarcinoma cells and cell lines, and in the invasive cells of melanocyticskin lesions where its expression correlates with tumor progression(Degen et al., 1998, Am. J. Pathol. 152:805-13; van Kempen et al., 2000,Am. J. Pathol. 156:769-74; Kristiansen et al., 2003, Prostate 54:34-43).Furthermore, overexpression of truncated CD166, which cannot mediatehomophilic cell interactions, promotes tissue invasion (van Kempen etal., 2001, J. Biol. Chem. 276:25783-90) suggesting CD166 plays a role inthe transition between cell clustering and cell movement.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of CD164 compared tonon-tumorigenic colon tumor cells. CD164 is a member of a family ofglycoprotein sialomucin receptors and is highly expressed by primitivehematopoietic progenitor cells where it is involved in adhesion ofprogenitor cells to the stroma and can act as a negative regulator ofprogenitor cell proliferation (Watt & Chan, 2000, Leuk. Lymphoma37:1-25).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of CD82 compared to non-tumorigeniccolon tumor cells. CD82 is a ubiquitously member of the tetraspaninsuperfamily that has been implicated in many cellular functionsincluding adhesion, migration, signal transduction, and differentiation(Maeker et al., 1997, FASEB J. 11:428-42). Like CD9 described in detailabove, CD82 acts as a suppressor of metastasis, with expression lower inmetastatic cells compared with a number of primary tumor (Liu et al.,2003, World J. Gastroenterol. 9:1231-6).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of transforming growth factor, betareceptor I (TGFBR1) compared to non-tumorigenic colon tumor cells. TheTGF-1 pathway regulates numerous processes including: cellularproliferation, adhesion and differentiation; hematopoiesis;inflammation; skeletal development and tissue homeostasis (Waite & Eng,2003, Nat. Rev. Genet. 4:763; Chen et al., 2004, Growth Factors22:233-41; He et al., 2005, Ann. N.Y. Acad. Sci. 1049:28-38).Deregulated TGF-1 signaling is implicated in a range of human diseasesincluding several cancers suggesting that carcinogenesis can proceed byusurping homeostatic mechanisms controlling normal development (Beachyet al., 2004, Nature 432:324).

TGFBR1 is the type 1 receptor for TGF-β isoforms. These secretedcytokines activate heteromeric complexes of type I and type IIserine/threonine kinase receptors. The type II receptor kinase isconstitutively active and upon ligand binding phosphorylates the type Ireceptor, activating a downstream signal through cytosolic SMADproteins. TGF-β isoforms act through receptor-regulated SMAD 2 and 3which in turn interact with a common partner SMAD, SMAD4, to regulatetranscription (Waite & Eng, 2003, Nat. Rev. Genet. 4:763).

The anti-mitogenic response of cells to TGF-β ligands suggests thatpathway components are tumor suppressors with inactivation of thepathway contributing to tumorigenesis (Itoh et al., 2000, Eur. J.Biochem. 267:6954). This has been confirmed in knock-out mice withSmad3-deficient mice developing metastatic colorectal cancer, Smad4heterozygous mice developing malignant intestinal tumors, andconditional Bmpr1 loss in the epidermis and hair follicles results inhair matrix cell hyperplasia (Zhu et al., 1998, Cell 94:703-14; Takakuet al., 1998, Cell 92:645-56; Ming Kwan et al., 2004, Genesis 39:10-25).In humans, Smad4 is mutated or inactivated in a number of cancersincluding pancreatic, colon, breast and lung cancers (Hahn et al., 1996,Science 271:350-3; Schutte et al., 1996, Cancer Res. 56:2527-30).Furthermore, germline mutations in the mothers against decapentaplegichomologue 4 gene (MADH4), which encodes SMAD4, and the BMP receptor typeIA gene (BMPR1A) are associated with 15-20% and 20-25%, respectively, ofjuvenile polyposis syndrome (JPS) cases, an autosomal dominant cancersyndrome characterized by gastrointestinal hamartomatous polyps and ahigh risk of gastrointestinal cancer (Howe et al., 1998, Science280:1086-8; Howe et al., 2001, Nat. Genet. 28:184-7; Zhou et al., 2001,Am. J. Hum. Genet. 69:704-11). The identification of TGFBR1 asupregulated in colon cancer stem cells suggests that targeting the TGF-βpathway can help eliminate tumorigenic cells responsible for theformation and reoccurrence of solid tumors.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of MET, a receptor tyrosine kinaseactivated by the secreted hepatocyte growth factor/scatter factor(HGF/SF), compared to non-tumorigenic colon tumor cells. MET controlscell proliferation, dissociation, and migration during embryogenesis andaberrant activation of these processes in human cancer contributes totumor growth and metastasis. MET activation phosphorylates beta-catenin,a modification that promotes loss of beta-catenin association withalpha-catenin at cell junctions and thus decreasing cellular adhesionand making beta-catenin available for Wnt mediated signaling, itselfassociated with carcinogenesis (Tokunou et al., 2001, Am. J. Pathol.158:1451; Birchmeier et al., 2003, Nat. Rev. Mol. Cell. Biol. 4:915;Biez, 2004, Curr. Biol. 15:R64; Boccaccio et al., 2005, Nature 434:396;and Ma et al., 2005, Cancer Res. 65:1479).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of ephrin-B2 (EFNB2) compared tonon-tumorigenic colon tumor cells. EFNB2 is a member of a family ofmembrane-bound ligands that interact with receptor tyrosine kinases, theEph receptors to generate a bi-directional cell-cell contact signalingsystem that directs cell migration, neural cell guidance andvasculogenesis. EFNB2 is a transmembrane ligand that binds to the EPHB4and EPHA3 receptors. Both Eph receptors and ephrin ligands areoverexpressed in a number of cancers, including breast, small-cell lung,and gastrointestinal cancer, melanomas, and neuroblastomas (Nakamoto &Bergemann, 2002, Microsc. Res. Tech. 59:58-67).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of integrin alpha 6 (ITGA6; CD49f),integrin alpha V (ITGAV) and integrin beta 1 (ITGB1) compared tonon-tumorigenic colon tumor cells. Integrins are integral cell-surfaceproteins that consist of both an alpha and a beta chain with chainsassociating with multiple partners to form different integrins.Integrins function in cellular adhesion and migration to reversiblyconnect cells to the extracellular matrix or to receptors on other cellsand thus can play a critical role in cancer invasion and metastasis.Integrin-mediated adhesion also affects intracellular signaling and canthus regulate cell survival, proliferation, and differentiation (Danen,2005, Curr. Pharm. Des. 11:881-91).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of teratocarcinoma-derived growthfactor 1 (TDGF1) or CRIPTO compared to non-tumorigenic colon tumorcells. TDGF1 is a GPI-linked protein with a single EGF-like motif and anovel cysteine-rich domain called the Cripto, FRL-1, and Cryptic (CFC)motif and acts as a coreceptor to recruit the TGF-β ligand, Nodal, tothe activin receptor (Yeo & Whitman, 2001, Mol. Cell. 7:949-57; Yan etal., 2002, Mol. Cell. Biol. 22:4439-49). TDGF1 and is highlyoverexpressed in a number of cancers including breast, pancreatic,ovarian and colon carcinomas (Salomon et al., 2000, Endocr. Relat.Cancer 7:199-226) and acts to block Activin B-mediated suppression ofcell proliferation suggesting an important role in carcinogenesis (Shen,2003, J. Clin. Invest. 112:500-2).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of heparin-binding EGF-like growthfactor (HBEGF) compared to non-tumorigenic colon tumor cells. HBEGF issynthesized as a membrane bound precursor protein and, similar to otherEGFR ligands, becomes active through release from the cell membrane byectodomain shedding (Massague et al., 1993, Annu Rev Biochem,62:515-41). HBEGF is a potent inducer of tumor growth and angiogenesis,and dysregulation of ectodomain shedding produces lethal hyperplasia inmice (Ongusaha et al., 2004, Cancer Res. 64:5283-90; Yamazaki et al.,2003, J. Cell Biol. 163:469-75).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of ABCC3 and ABCC4 compared tonon-tumorigenic colon tumor cells. ABCC3 and ABCC4 are members of theATP-binding cassette transporter superfamily and the MRP subfamilyinvolved in multi-drug resistance by reducing the concentration ofintracellular drugs. The increased expression of these transporters incolon cancer stem cells suggests a mechanism by which these cells evadechemotherapies leading to cancer reoccurrence and can serve as usefultargets to render cancer stem cells vulnerable to such drugs.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of TDE2 compared to non-tumorigeniccolon tumor cells. TDE2 has sequence similarity to the mouse testiculartumor-differentially-expressed (Tde1) gene and was identified as a geneupregulated in non-small cell lung cancers (Player et al., 2003, Int. J.Cancer 107:238-43).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of TNFRSF21 compared tonon-tumorigenic colon tumor cells. TNFRSF21 is a member of the tumornecrosis factor receptor superfamily, which is critically involved inthe regulation of inflammation, immune response, and lymphoid tissuehomeostatsis (Smith et al., 1994, Cell 76:959-62; Locksley et al., 2001,Cell 104:487-501). TNFRSF21 can activate NFkappaB and MAPK8/JNK andinduce cell apoptosis. Furthermore, knockout studies demonstrateTNFRSF21 acts as an important regulator of CD4+ T cell proliferation, Thdifferentiation, B cell activation and humoral immune responses (Liu etal., 2001, Immunity 15:23-34; Zhao et al., 2001, J. Exp. Med.194:1441-8; Schmidt et al., 2003, J. Exp. Med. 197:51-62).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels KIAA1324 compared tonon-tumorigenic colon tumor cells. KIAA1324 is a putative cell-surfaceprotein.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of SOX4 or SRY (sex determiningregion Y)-box 4 compared to non-tumorigenic colon tumor cells. SOX(SRY-related HMG box) family member gene products are critical toembryonic developmental and cell fate determination duringorganogenesis. The best defined system for the role of SOX4 inorganogenesis is in brain development (Wegner & Stolt, 2005, TrendsNeurosci, 28:583-8). Elevated SOX4 expression has also been correlatedwith increased survival of tumor cells in a number of tumor types,including, but not limited to, bladder and prostate cancer (Aaboe etal., 2006, Cancer Res, 66:3434-42; Liu et al., 2006, Cancer Res,66:4011-9; Pramoonjago et al., 2006, Oncogene, 25:5626-39).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of atonal homolog 1 (ATOH1)compared to non-tumorigenic colon tumor cells. ATOH1 is a basichelix-loop-helix (BHLH) family transcription factor thought to be atarget of the Wnt signaling pathway (Loew et al., 2005, Ann N Y AcadSci, 1059:174-83). Its tight regulation of ATOH1 expression is importantfor normal colonic development (Loew et al., 2005, Ann N Y Acad Sci,1059:174-83; Mutoh et al., 2006, Differentiation, 74:313-21).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of E-cadherin (CDH1) compared tonon-tumorigenic colon tumor cells. CDH1 encodes a classical,calcium-dependent glycoprotein cadherin involved in cell-cell adhesion(Cavallaro & Christofori, 2004, Nat Rev Cancer, 4:118-32). Altered CDH1expression, or mutations, result in tumorigenesis in a number of organs,and tumor aggressiveness has been correlated with loss of functionalCDH1 (Georgolios et al., 2006, J Exp Clin Cancer Res, 25:5-14; Katoh,2005, Int J Oncol, 27:1677-83; Cowin et al., 2005, Curr Opin Cell Biol,17:499-508; Charalabopoulos et al., 2004, Exp Oncol, 26:256-60).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of Eph receptor B2 (EPHB2) comparedto non-tumorigenic colon tumor cells. Ephrin receptors respond to theirligands, the ephrins, to regulate a number of tissue developmentalprocesses, including gut organization, bone formation, and CNSregeneration (Crosnier et al., 2006, Nat Rev Genet, 7:349-59; Mundy &Elefteriou., 2006, Cell, 126:441-3; Klein, 2004, Curr Opin Cell Biol,16:580). Of interest, altered EphB2 expression or function has beencorrelated with aggressiveness in neoplasias of the gut and prostate(Kokko et al., 2006, BMC Cancer, 6:145; Batlle et al., 2005, Nature,435:1126-30; Huusko et al., 2004, Nat Genet, 36:979-83; Kataoka et al.,2002, J Cancer Clin Oncol, 128:343-8).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of v-myb myeloblastosis viraloncogene homolog (MYB) compared to non-tumorigenic colon tumor cells.MYB has been identified as an oncogene in pancreatic cancer and alsoplays a significant role in cell fate decisions during hematopoeiticdevelopment (Maitra et al., 2006, Best Pract Res Clin Gastroenterol,20:211-26; Sakamoto et al., 2006, Blood, 108:896-903; Ramsay, 2005,Growth Factors, 23:253-61). Overexpression of MYB may facilitatetumorigenesis by increasing the expression of genes that promotesurvival in low oxygen and nutrient conditions (Ramsay et al., 2005, IntJ Biochem Cell Biol, 37:1254-68; Xu et al., 2003, Am J Physiol CellPhysiol, 284:c1262-71).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of (MYC) compared tonon-tumorigenic colon tumor cells. Myc is a strong oncogene thatpromotes cell cycle progression and transformation, and itsoverexpression has been observed in many tumors (Vita & Henriksson,2006, Semin Cancer Biol, 16:318-30; Wade & Wahl, 2006, Curr TopMicrobiol Immunol, 302:169-203). Myc is a target of nuclear β-cateninand is upregulated in a large proportion of colon tumors, especiallytumors with mutated APC and strong nuclear β-catenin signaling (Liu etal., 2006, Adv Anat Pathol, 13:270-4; Reichling et al., 2005, CancerRes, 65:166-76).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of SRY-box 9 (SOX9) compared tonon-tumorigenic colon tumor cells. SOX9 is believed to be important forcell fate decisions during organogenesis. In particular, SOX9 plays animportant role in chondrogenesis and testicular maturation (Hardinghamet al., 2006, J Anat, 209:469; Kobayashi et al., 2005, Ann N Y Acad Sci,1061:9-17). SOX9 is an important intestinal crypt differentiation factor(Blache et al., 2004, J Cell Biol, 166:37-47) and represses the CDX2 andMUC2 genes, normally expressed in mature villus cells. Repression ofdifferentiation in this manner may promote accumulation ofundifferentiated intestinal cells, manifesting as neoplasia.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of serine/threonin kinase receptorassociated protein (STRAP) compared to non-tumorigenic colon tumorcells. STRAP is a WD40 repeat protein that mediates TGF-β signaling viaPDK1 in a phosphatidylinositol 3-kinase dependent manner (Seong et al.,2005, J Biol Chem, 280:42897-908). STRAP may also mediated repression ofTGF-β signaling, as it recruits the inhibitory Smad7 protein to type Iand II TGF-β receptors (Datta & Moses, 2000, Mol Cell Biol, 20:3157-67).Not only has STRAP amplification been observed in colorectal cancer(Buess et al., 2004, Neoplasia, 6:813-20), but STRAP has recently beendescribed as an oncogene that is up-regulated in 60% of colon and 78% oflung carcinomas (Halder et al., 2006, Cancer Res, 66:6156-66).

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of CD59 compared to non-tumorigeniccolon tumor cells. CD59 binds to complement C8 and C9 components,thereby inhibiting complement-mediated lysis (Longhi M P, Harris C L,Morgan B P, Gallimore A. Trends Immunol. (2006) 27:102-108; Cole D S,Morgan B P. Clin Sci (Lond) (2003) 104:455-466). Because of this role,it is also known as membrane inhibitor of reactive lysis (MIRL) ormembrane-attack-complex-inhibitory factor (MACIF). Its molecular weightis ˜19 kDa and is a GPI-linked glycoprotein expressed on a variety ofcell types, including hematopoietic and non-hematopoietic cells.Recently, CD59 has been shown to modulate adaptive immune responses byinhibiting CD4⁺ T-cell activation (Longhi M P, Harris C L, Morgan B P,Gallimore A. Trends Immunol. (2006) 27:102-108). As a result of thesefunctions, higher expression of CD59 on colon cancer stem cells maypromote cell survival by diminishing T-cell responses to abnormalantigen presentation by MHC class II molecules and preventing complementmediated lysis (Knutson K L, Disis M L., Curr Drug Targets Immune EndocrMetabol Disord. (2005) 5:365-371). In support of this argument,resistance to Rituximab can be overcome when neutralizing CD59antibodies are present (Cerny T, Borisch B, Introna M, Johnson P, Rose AL., Anticancer Drugs. (2002) 13 Suppl 2:S3-10). Furthermore, CD59 mRNAexpression is higher in metastatic vs. non-metastatic prostate cancercells (Loberg R D, Wojno K J, Day L L, Pienta K J., Urology. (2005)66:1321-1326), and may provide metastatic cells with a protectiveadvantage. Finally, Prod 1, a newt orthologue of mammalian CD59, hasbeen demonstrated to have an important role in tissue patterning duringappendage regeneration (Brockes J P, Kumar A., Science (2005)310:1919-1923). These studies suggest that CD59 has an important role intumorigenesis via enhancement of survival, immune-response evasion andstem cell biology.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises repressed levels of transcription factor 4 (TCF4)compared to non-tumorigenic colon tumor cells. TCF4 is a basichelix-loop-helix (bHLH) transcription factor that recognizesEphrussi-box (E-box) binding sites and activates transcription whencomplexed with other TCF family members and β-catenin (Barker et al.,2000, Adv Cancer Res, 77:1-24). Constitutive TCF4/β-catenin complexesare thought to be present in the majority of colon tumors due to APCmutations and constitutive nuclear localization of β-catenin (Clevers,2004, Cancer Cell, 5:5-6). This interaction results in dysregulation ofmany genes, including MYC, and a proliferative phenotype. Whiledisruption of this complex can reverse the proliferative phenotype, theeffect of reduced TCF4 for β-catenin association and action in thenucleus is unknown.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises repressed levels of vimentin (VIM) compared tonon-tumorigenic colon tumor cells. Vimentin is an intermediate filamentpredominantly present in mesenchymal tissue. In benign hyperplasticcolon polyps, vimentin is consistently present and is likely a marker ofdifferentiated colon cells (Groisman et al., 2006, Histopathology,48:431-7). VIM has been identified as a target of TCF4/β-catenincomplexes (Gilles et al., 2003, Cancer Res, 63:2658-64), and thus itsrepressed expression in TG cells may correlate with reduced levels ofTCF4 (see above). It is also of interest that the epithelial tomesenchymal switch that accompanies aggressive and metastatic phenotypesof many tumors is characterized by a loss of E-cadherin and increase invimentin expression (Huber et al., 2005, Curr Opin Cell Biol, 17:1-11).Thus the opposite expression profile in most TG vs NTG profiles mayreflect the early stage of colon cancer stem cells in the progression toan advanced and aggressive disease state.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of BMPR1A compared tonon-tumorigenic colon tumor cells.

In certain embodiments of the present invention, colon cancer stem cellsexpression comprises elevated levels of ALDH activity.

(1) The BMP Signaling Pathway and Cancer

Bone morphogenetic proteins (BMPs) are multi-functional growth factorsof the transforming growth factor-β (TGF-β superfamily. The TGF-βpathway regulates numerous processes including: cellular proliferation,adhesion and differentiation; hematopoiesis; inflammation; skeletaldevelopment and tissue homeostasis with BMP signaling playing criticalroles in heart, neural and cartilage development, postnatal boneformation, and regulation of hematopoietic and intestinal stem cellbehavior (Waite & Eng, 2003, Nat. Rev. Genet. 4:763; Chen et al., 2004,Growth Factors 22:233-41; He et al., 2005, Ann. N.Y. Acad. Sci.1049:28-38). Deregulated TGF-β signaling is implicated in a range ofhuman diseases including several cancers suggesting that carcinogenesismay proceed by usurping homeostatic mechanisms controlling normaldevelopment and tissue repair by stem cell populations (Beachy et al.,2004, Nature 432:324).

Members of the TGF-β family include the structurally related TGF-βisoforms, activins and BMPs. These secreted cytokines activateheteromeric complexes of type I and type II serine/threonine kinasereceptors. The type II receptor kinase is constitutively active and uponligand binding phosphorylates the type I receptor, activating adownstream signal through cytosolic SMAD proteins. BMPs act throughreceptor-regulated SMAD 1, 5 and 8 which in turn interact with a commonpartner SMAD, SMAD4, to regulate transcription (Waite & Eng, 2003, Nat.Rev. Genet. 4:763).

The anti-mitogenic response of cell to TGF-β ligands suggests thatpathway components are tumor suppressors with inactivation of thepathway contributing to tumorigenesis (Itoh et al., 2000, Eur. J.Biochem. 267:6954). This has been confirmed in knock-out mice withSmad3-deficient mice developing metastatic colorectal cancer, Smad4heterozygous mice developing malignant intestinal tumors, andconditional Bmpr1 loss in the epidermis and hair follicles results inhair matrix cell hyperplasia (Zhu et al., 1998, Cell 94:703-14; Takakuet al., 1998, Cell 92:645-56; Ming Kwan et al., 2004, Genesis 39:10-25).In humans, Smad4 is mutated or inactivated in a number of cancersincluding pancreatic, colon, breast and lung cancers (Hahn et al., 1996,Science 271:350-3; Schutte et al., 1996, Cancer Res. 56:2527-30).Furthermore, germline mutations in the mothers against decapentaplegichomologue 4 gene (MADH4), which encodes SMAD4, and the BMP receptor typeIA gene (BMPR1A) are associated with 15-20% and 20-25%, respectively, ofjuvenile polyposis syndrome (JPS) cases, an autosomal dominant cancersyndrome characterized by gastrointestinal hamartomatous polyps and ahigh risk of gastrointestinal cancer (Howe et al., 1998, Science280:1086-8; Howe et al., 2001, Nat. Genet. 28:184-7; Zhou et al., 2001,Am. J. Hum. Genet. 69:704-11).

Though BMP ligands commonly act as negative regulators of cellproliferation and tumor growth (Miyazaki et al., 2004, Oncogene23:9326-35; Nishanian et al., 2004, Cancer Biol. Ther. 3:667-75; Wen etal., 2004, Biochem. Biophys. Res. Commun. 26:100-6; Baada Ro et al.,2004 Oncogene 23:3024-32), activation of the BMP pathway may play a rolein certain cancers. Expression of BMPR1B has been implicated in theprogression and dedifferentiation of oestrogen positive breast cancers(Helms et al., 2005, J. Pathol. 206:366-76) and expression of BMPligands may promote growth of human breast, pancreatic and prostatecancer cells and prevent apoptosis and hypoxic death of cancer cells(Raida et al., 2005, Int. J. Oncol. 26:1465-70; Pouliot et al., 2003,63:277-81; Kleeff et al., 1999, Gastroenterology 116:1202-16; Ide etal., 1997, Cancer Res. 57:5022-7; Chen et al., 2001, J. Biol. Chem.276:39259-63; Izumi et al., 2001, J. Biol. Chem. 276:31133-41).

BMP signaling is also involved in vascular development and angiogenesis.BMP-2 enhances neovascularization of developing tumors (Langenfeld &Langenfeld, 2004, Mol. Cancer. Res. 2:141-9), and BMP-7 induces vascularendothelial growth factor (VEGF) in prostate cancer cell linessuggesting a contribution of BMPs to osteoblastic metastases (Dai etal., 2004, Cancer Res. 64:994-9). In humans, germline loss of functionmutations in the BMP receptor type II (BMPR2) gene produce an autosomaldominant vascular disorder known as primary pulmonary hypertension(PPH). PPH is characterized by the loss of small pulmonary arteries andarterioles resulting in persistent elevation of pulmonary vascularresistance, pulmonary hypertension and heart failure. Pulmonary vascularendothelial hyperproliferation is observed in PPH patients, suggestingthat some BMP ligands may act as vascular growth suppressors (Waite &Eng, 2003, Nat. Rev. Genet. 4:763).

The identification of BMPR1A as upregulated in colon cancer stem cellssuggests that targeting the BMP pathway may help eliminate tumorigeniccells responsible for the formation and reoccurrence of solid tumors.Furthermore, because of the prominent role of angiogenesis in tumorformation and maintenance, targeting the BMP pathway may also inhibitangiogenesis, starving a cancer of nutrients and contributing to itselimination.

In other embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of the Wnt receptor FZD6 comparedto non-tumorigenic colon tumor cell. In yet other embodiments of thepresent invention, colon cancer stem cell expression comprises elevatedlevels of the Wnt receptor FZD7 compared to non-tumorigenic colon tumorcell

(2) The Wnt Signaling Pathway and Cancer

The Wnt signaling pathway is one of several critical regulators ofembryonic pattern formation, post-embryonic tissue maintenance, and stemcell biology. More specifically, Wnt signaling plays an important rolein the generation of cell polarity and cell fate specification includingself-renewal by stem cell populations. Unregulated activation of the Wntpathway is associated with numerous human cancers where it may alter thedevelopmental fate of tumor cells to maintain them in anundifferentiated and proliferative state. Thus carcinogenesis mayproceed by usurping homeostatic mechanisms controlling normaldevelopment and tissue repair by stem cells (reviewed in Reya & Clevers,2005, Nature 434:843; Beachy et al., (04) Nature 432:324).

The Wnt signaling pathway was first elucidated in the Drosophiladevelopmental mutant wingless (wg) and from the murine proto-oncogeneint-1, now Wnt1 (Nusse & Varmus, 1982, Cell 31:99-109; Van Ooyen &Nusse, 1984, Cell 39:233-40; Cabrera et al., 1987, Cell 50:659-63;Rijsewijk et al., 1987, Cell 50:649-57). Wnt genes encode secretedlipid-modified glycoproteins of which 19 have been identified inmammals. These secreted ligands activate a receptor complex consistingof a Frizzled (Fzd) receptor family member and low-density lipoprotein(LDL) receptor-related protein 5 or 6 (LPR5/6). The Fzd receptors areseven transmembrane domain proteins of the G-protein coupled receptor(GPCR) superfamily and contain a large extracellular N-terminal ligandbinding domain with 10 conserved cysteins, known as a cysteine-richdomain (CRD) or Fzd domain. Different Fzd CRDs have different bindingaffinities for specific Wnts (Wu & Nusse, 2002, J. Biol. Chem.277:41762-9), and Fzd receptors have been grouped into those thatactivate the canonical β-catenin pathway and those that activatenon-canonical pathways described below (Miller et al., 1999, Oncogene18:7860-72). FZD6 and FZD7 are two of ten identified human Wntreceptors. LRP5/6 are single pass transmembrane proteins with fourextracellular EGF-like domains separated by six YWTD amino acid repeatsthat contribute to Fzd and ligand binding (Johnson et al., 2004, J. BoneMineral Res 19:1749).

The canonical Wnt signaling pathway activated upon receptor binding ismediated by the cytoplasmic protein Dishevelled (Dsh) interactingdirectly with the Fzd receptor and results in the cytoplasmicstabilization and accumulation of β-catenin. In the absence of a Wntsignal, β-catenin is localized to a cytoplasmic destruction complex thatincludes the tumor suppressor proteins adenomatous polyposis coli (APC)and auxin. These proteins function as critical scaffolds to allowglycogen synthase kinase (GSK)-3β to bind and phosphorylate β-catenin,marking it for degradation via the ubiquitin/proteasome pathway.Activation of Dsh results in phosphorylation of GSK3β and thedissociation of the destruction complex. Accumulated cytoplasmicβ-catenin is then transported into the nucleus where it interacts withthe DNA-binding proteins of the Tcf/Lef family to activatetranscription.

In addition to the canonical signaling pathway, Wnt ligands also activeβ-catenin-independent pathways (Veeman et al., 2003, Dev. Cell5:367-77). Non-canonical Wnt signaling has been implicated in numerousprocesses but most convincingly in gastrulation movements via amechanism similar to the Drosophila planar cell polarity (PCP) pathway.Other potential mechanisms of non-canonical Wnt signaling includecalcium flux, JNK, and both small and heterotrimeric G-proteins.Antagonism is often observed between the canonical and non-canonicalpathways, and some evidence indicates that non-canonical signaling maysuppress cancer formation (Olson & Gibo, 1998, Exp. Cell Res. 241:134;Topol et al., 2003, J. Cell Biol. 162:899-908).

Hematopoietic stem cells (HSCs) are the best understood stem cells inthe body, and Wnt signaling is implicated both in their normalmaintenance as well as in leukemic transformation (Reya & Clevers, 2005,Nature 434:843). HSCs are a rare population of cells that reside in astomal niche within the adult bone marrow. These cells are characterizedboth by a unique gene expression profile as well as an ability tocontinuously give rise to more differentiated progenitor cells toreconstitute the entire hematopoietic system. Both HSCs and the cells oftheir stromal microenvironment express Wnt ligands, and Wnt reporteractivation is present in HSCs in vivo. Furthermore, both 3-catenin andpurified Wnt3A promote self-renewal of murine HSCs in vitro and enhancetheir ability to reconstitute the hematopoietic system in vivo whileWnt5A promotes expansion of human hematopoietic progenitors in vitro andre-population in a NOD-SCID xenotransplant model (Reya et al., 2003,Nature 423:409-14; Willert et al., 2003, Nature 423:448-52; Van Den Berget al., 1998, Blood 92:3189-202; Murdoch et al., 2003, PNAS 100:3422-7).

More recently Wnt signaling has been found to play a role in theoncogenic growth of both myeloid and lymphoid lineages. For example,granulocyte-macrophage progenitors (GMPs) from chronic myelogenousleukemias display activated Wnt signaling on which they are depended forgrowth and renewal (Jamieson et al., 2004, N. Engl. J. Med. 351:657-67)And while leukemias do not appear to harbor mutations within the Wntpathway, autocrine and/or paracrine Wnt signaling may sustain cancerousself-renewal (Reya & Clevers 2005, Nature 434:843).

The canonical Wnt signaling pathway also plays a central role in themaintenance of stem cell populations in the small intestine and colon,and the inappropriate activation of this pathway plays a prominent rolein colorectal cancers (Reya & Clevers, 2005, Nature 434:843). Theabsorptive epithelium of the intestines is arranged into villi andcrypts. Stem cells reside in the crypts and slowly divide to producerapidly proliferating cells which give rise to all the differentiatedcell populations that move up out of the crypts to occupy the intestinalvilli. The Wnt signaling cascade plays a dominant role in controllingcell fates along the crypt-villi axis and is essential for themaintenance of the stem cell population. Disruption of Wnt signalingeither by genetic loss of Tcf7/2 by homologous recombination (Korinek etal., 1998, Nat. Genet. 19:379) or overexpression of Dickkopf-1 (Dkk1), apotent secreted Wnt antagonist (Pinto et al., 2003, Genes Dev.17:1709-13; Kuhnert et al., 2004, PNAS 101:266-71), results in depletionof intestinal stem cell populations.

Colorectal cancer is most commonly initiated by activating mutations inthe Wnt signaling cascade. Approximately 5-10% of all colorectal cancersare hereditary with one of the main forms being familial adenomatouspolyposis (FAP), an autosomal dominant disease in which about 80% ofaffected individuals contain a germline mutation in the adenomatouspolyposis coli (APC) gene. Mutations have also been identified in otherWnt pathway components including auxin and β-catenin. Individualadenomas are clonal outgrowths of epithelial cell containing a secondinactivated allele, and the large number of FAP adenomas inevitablyresults in the development of adenocarcinomas through addition mutationsin oncogenes and/or tumor suppressor genes. Furthermore, activation ofthe Wnt signaling pathway, including gain-of-function mutations in APCand β-catenin, can induce hyperplastic development and tumor growth inmouse models (Oshima et al., 1997, Cancer Res. 57:1644-9; Harada et al.,1999, EMBO J. 18:5931-42).

A role for Wnt signaling in cancer was first uncovered with theidentification of Wnt1 (originally int1) as an oncogene in mammarytumors transformed by the nearby insertion of a murine virus (Nusse &Varmus, 1982, Cell 31:99-109). Additional evidence for the role of Wntsignaling in breast cancer has since accumulated. For instance,transgenic overexpression of β-catenin in the mammary glands results inhyperplasias and adenocarcinomas (Imbert et al., 2001, J. Cell Biol.153:555-68; Michaelson & Leder, 2001, Oncogene 20:5093-9) whereas lossof Wnt signaling disrupts normal mammary gland development (Tepera etal., 2003, J. Cell Sc. 116:1137-49; Hatsell et al., 2003, J. MammaryGland Biol. Neoplasia 8:145-58). More recently mammary stem cells havebeen shown to be activated by Wnt signaling (Liu et al., 2004, PNAS101:4158). In human breast cancer, β-catenin accumulation implicatesactivated Wnt signaling in over 50% of carcinomas, and though specificmutations have not been identified, upregulation of Frizzled receptorexpression has been observed (Brennan & Brown, 2004, J. Mammary GlandNeoplasia 9:119-31; Malovanovic et al., 2004, Int. J. Oncol.25:1337-42).

In other embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of Carcinoembryonic antigen-relatedcell adhesion molecule 6 (CEACAM6; CD66c; NCA) compared tonon-tumorigenic colon tumor cells. CEACAM6 is aglycophosphatidylinositol (GPI) anchored immunoglobulin superfamilymember found in higher primates that is thought to mediate intercellularinteractions (Yasui et al., 2004 Cancer Sci 95:385-92). CEACAM6 ispredominantly expressed in the colon where it is a potential target ofthe TCF-1 transcription factor in colonic crypts where stem cells arebelieved to reside (Scholzel et al., 2000, Am. J. Pathol. 156:595-605;Liebig et al., 2005, Cancer Lett. 223:159-67; Roose et al., 1999,285:1923-6). CEACAM6 expression has also been detected in neutrophils.However, whereas other family members, such as CEACAM5 (which also showsincreased in expression in colon cancer stem cells) mediate NK-cellinhibitory interactions via CEACAM1 on NK-cells, CEACAM6 does not appearto have this activity (Market et al., 2004, J. Immunol. 173:3732-9)

CEACAM6 is overexpressed in a number of gastrointestinal malignancies(Yasui et al., 2004 Cancer Sci 95:385-92), including colorectal andpancreatic cancers, and this expression correlates with aggressive(usually non-differentiated) tumors (Kodera et al., 1993, Br. J. Cancer68:130-6; Ilantzis et al., 2002, Neoplasia 4:151-63) in which a highpercentage of cancer stem cells are thought to reside. CEACAM6expression is also highest at the invasion front (Liebig et al., 2005,Cancer Lett. 223:159-67), again the location within colon tumors wherewe believe cancer stem cells reside. Upregulation of CEACAM6 expressionin hyperplastic polyps and early adenomas represents one of the earliestobservable molecular events leading to colorectal tumors (Yasui et al.,2004 Cancer Sci 95:385-92), and CEACAM6 expression as an independentmarker predicts poor overall survival and disease-free survival(Jantscheff et al., 2003, J. Clin. Oncol. 21:3638-46). Ectopicexpression of CEACAM6 facilitates anchorage-independent growth in vitro(i.e. survival) and greater metastatic ability in vivo (Duxbury et al.,2004, Oncogene 23:465-73). Furthermore, repression of CEACAM6 geneexpression by siRNA in chemoresistance pancreatic cancer cell linesrenders them susceptible to chemotherapy and anoikis, and in vivoprevents liver metastasis (Whang et al., 2005, Annals of Surgery240:667). Resistance to chemotherapy and anoikis appears to be mediatedby c-Src, FAK and Akt, all downstream mediators of integrin signalingsuggesting crosstalk between CEACAM6 and the integrins (Duxbury et al.,2004. Biochem Biophys. Res. Commun. 317:133-141; Duxbury et al., 2004,J. Biol. Chem. 279:23176-82). Interestingly integrin expression issignificantly higher in tumorigenic vs. nontumorigenic colon tumorcells, as are a number of mediators of integrin signaling includingmembers of the Src-family kinase family. It is possible that high levelsof CEACAM6 stimulate non-canonical β-catenin activation in coordinationwith the integrins, potentially circumventing requirements for canonicalβ-catenin activation via Wnts and Frizzled receptors.

In certain embodiments of the present invention, colon cancer stem cellexpression comprises elevated levels of Notch2 compared tonon-tumorigenic colon tumor cells. In other embodiments, colon cancerstem cell expression comprises elevated levels the of Notch ligand JAG1compared to non-tumorigenic colon tumor cells. In other embodiments,colon cancer stem cell expression comprises elevated levels of HES1 andHES6, which are Notch signaling pathway target genes, compared tonon-tumorigenic colon tumor cells. The identification of Notch2, JAG1,Hes1 and Hes6 as upregulated in colon cancer stem cells suggest a rolefor Notch signaling in colon cancer stem cell biology and cancer.

(3) The Notch Signaling Pathway and Cancer

The Notch signaling pathway is one of several critical regulators ofembryonic pattern formation, post-embryonic tissue maintenance, and stemcell biology. More specifically, Notch signaling is involved in theprocess of lateral inhibition between adjacent cell fates and plays animportant role in cell fate determination during asymmetric celldivisions. Unregulated Notch signaling is associated with numerous humancancers where it may alter the developmental fate of tumor cells tomaintain them in an undifferentiated and proliferative state (Brennanand Brown, 2003, Breast Cancer Res. 5:69). Thus carcinogenesis mayproceed by usurping homeostatic mechanisms controlling normaldevelopment and tissue repair by stem cell populations (Beachy et al.,2004, Nature 432:324).

The Notch receptor was first identified in Drosophila mutants withhaploinsufficiency resulting in notches at the wing margin whereasloss-of-function producing an embryonic lethal “neurogenic” phenotypewhere cells of the epidermis switch fate to neural tissue (Moohr, 1919,Genet. 4:252; Poulson, 1937, PNAS 23:133; Poulson, 1940, J. Exp. Zool.83:271). The Notch receptor is a single-pass transmembrane receptorcontaining numerous tandem epidermal growth factor (EGF)-like repeatsand cysteine-rich Notch/LIN-12 repeats within a large extracellulardomain (Wharton et al., 1985, Cell 43:567; Kidd et al., 1986, Mol. Cell.Biol. 6:3094; reviewed in Artavanis-Tsakonas et al., 1999, Science284:770). Four mammalian Notch proteins have been identified, andmutations in these receptors invariably result in developmentalabnormalities and human pathologies including several cancers asdescribed in detail below (Gridley, 1997, Mol. Cell. Neurosci. 9:103;Joutel & Tournier-Lasserve, 1998, Semin. Cell Dev. Biol. 9:619-25).

The Notch receptor is activated by single-pass transmembrane ligands ofthe Delta, Serrated, Lag-2 (DSL) family. There are five known Notchligands in mammals: Delta-like 1 (D111), Delta-like 3 (D113), Delta-like4 (D114), Jagged 1 and Jagged 2 characterized by a DSL domain and tandemEGF-like repeats within the extracellular domain. The extracellulardomain of the Notch receptor interacts with that of its ligands,typically on adjacent cells, resulting in two proteolytic cleaveages ofNotch, one extracellular mediated by an ADAM protease and one within thetransmembrane domain mediated by gamma secretase. This latter cleavagegenerates the Notch intracellular domain (NICD), which then enters thenucleus where it activates the CBF1, Suppressor of Hairless [Su(H)],Lag-2 (CSL) family of transcription factors (or RBP-J) as the majordownstream effectors to increase transcription of nuclear basichelix-loop-helix transcription factors of the Hairy and Enhancer ofSplit [E(spl)] family (Artavanis-Tsakonas et al., 1999, Science 284:770;Brennan and Brown, 2003, Breast Cancer Res. 5:69; Iso et al., 2003,Arterioscler. Thromb. Vasc. Biol. 23:543).

Hematopoietic stem cells (HSCs) are the best understood stem cells inthe body, and Notch signaling is implicated both in their normalmaintenance as well as in leukemic transformation (Kopper & Hajdu, 2004,Pathol. Oncol. Res. 10:69-73). HSCs are a rare population of cells thatreside in a stomal niche within the adult bone marrow. These cells arecharacterized both by a unique gene expression profile as well as anability to continuously give rise to more differentiated progenitorcells to reconstitute the entire hematopoietic system. Constitutiveactivation of Notch1 signaling in HSCs and progenitors cells establishesimmortalized cell lines that generate both lymphoid and myeloid cells invitro and in long-term reconstitution assays (Varnum-Finney et al.,2000, Nat. Med. 6:1278-81), and the presence of Jagged 1 increasesengraftment of human bone marrow cell populations enriched for HSCs(Karanu et al., 2000, J. Exp. Med. 192:1365-72). More recently, Notchsignaling has been demonstrate in HSCs in vivo and shown to be involvedin inhibiting HSC differentiation. Furthermore, Notch signaling appearsto be required for Wnt-mediated HSC self-renewal (Duncan et al., 2005,Nat. Immunol. 6:314).

The Notch signaling pathway also plays a central role in the maintenanceof neural stem cells is implicated both in their normal maintenance aswell as in brain cancers (Kopper & Hajdu, 2004, Pathol. Oncol. Res.10:69-73; Purow et al., 2005, Cancer Res. 65:2353-63; Hallahan et al.,2004, Cancer Res. 64:7794-800). Neural stem cells give rise to allneuronal and glial cells in the mammalian nervous system duringdevelopment, and more recently have been identified in the adult brain(Gage, 2000, Science 287:1433-8). Mice deficient for Notch1; the Notchtarget genes Hes1, 3, and 5; and a regulator of Notch signalingpresenilin1 (PS1) show decreased numbers of embryonic neural stem cells.Furthermore, adult neural stem cells are reduced in the brains of PS1heterozygote mice (Nakamura et al., 2000, J. Neurosci. 20:283-93;Hitoshi et al., 2002, Genes Dev. 16:846-58). The reduction in neuralstem cells appears to result from their premature differentiation intoneurons (Hatakeyama et al., 2004, Dev. 131:5539-50) suggesting thatNotch signaling regulates neural stem cell differentiation andself-renewal.

In the gastrointestinal track, it is the Wnt signaling pathway thatappears to play the major role in maintaining stem cell populations andin controlling cell fate along the crypt-villus axis. Furthermore,inappropriate activation of the Wnt pathway plays a prominent role incolorectal cancers (Reya & Clevers, 2005, Nature 434:843). Here Notchsignaling is involved in inhibiting stem cell differentiation intonon-secretory absorptive enterocytes cells and promoting differentiationof secretory cell types, including enteroendocrines and goblet cells(Schonhoff et al., 2004, Endocrinol. 145:2639-44), and new evidencesuggests that Notch signaling may also be required for the maintenanceof stem cells (van Es et al., 2005, Nature, 435:959). Specifically,activation of Notch signaling by transgenic expression of the Notchintracellular domain in the intestinal epithelium blocks secretory celldifferentiation and expands the progenitor cell population (Fre et al.,2005, Nature 435). Conversely, conditional loss of the common Notchactivated transcription factor CSL/RBP-J in the intestines or treatmentwith a gamma-secretase inhibitor, both of which abolish Notch signaling,result in a rapid and extensive conversion of proliferative crypt cellsinto goblet cell, and gamma-secretase inhibitors could also convertproliferative adenoma cells into post-mitotic goblet cells in a mousemodel of colon cancer (van Es et al., 2005, Nature, 435:959).Furthermore, the Notch activated Hairy and Enhancer of Split [E(spl)]family transcription factor Hes6 is expressed in the proliferative celldomain and lost in the absence of CSL/RBP-J suggesting that Hes6 mayregulate intestinal epithelial cell fate decisions and stem cellmaintenance downstream of Notch (van Es et al., 2005, Nature, 435:959).Hes6 has been identified as a gene upregulated in both colon metastasesand in primary tumors derived from the lung, breast, and kidney(Swearingen et al., 2003, Cancer Lett. 198:229-39). The identificationby the present invention of the upregulation of Hes6 as a colon cancerstem cells, and thus as a colon cancer stem cell marker, suggests itsuse in characterizing, diagnosing, and treating colon cancers.

(4) Aldehyde Dehydrogenase

Intracellular aldehyde dehydrogenases (ALDH) enzymes oxidize aldehydesto carboxylic acids and carry out various catabolic processes, includingethanol and amine catabolism and conversion of vitamin A to retinoicacid (Labrecque J, Bhat P V, Lacroix A., Biochem Cell Biol. (1993)71:85-89; Russo J E, Hilton J., Cancer Res. (1988) 48:2963-2968). Highlevels of the ALDH enzyme protect hematopoietic stem cells (HSC) andintestinal crypt cells from the cytotoxic effects of cyclophosphamide(CPA) in procedures that purge grafts of tumor cells (Colvin O M,Pharmacological Purging of the Bone Marrow (2d ed.) Blackwell SciencesInc. (1999); Russo J E, Hilton J, Colvin O M, Prog. Clin. Biol. Res.(1989) 290:65-79). Because of high ALDH activity in HSC (Kastan M B,Schlaffer E, Russo J E, Colvin O M, Civin C I, Hilton J, Blood (1990)75:1947-1950), fluorescent ALDH substrates can be used for HSCpurification (Storms R W, Trujillo A P, Springer J B, et al., Proc.Natl. Acad. Sci. USA. (1999) 96:9118-9123). Specifically, Aldefluor™(StemCo Biomedical; Durham, N.C.), a non-toxic ALDH substrate consistingof a BODIPY-conjugated aminoacetaldehyde, can be used in conjunctionwith fluorescence activated cell sorting (FACS) through the combinationof ALDH-dependent increases in Aldefluor™ fluorescence with the low sidescatter characteristics of stem cell populations such as HSC and neuralstem cells (Cai J, Cheng A, Luo Y, et al., J, Neurochem. (2004)88:212-226).

Humans have nineteen ALDH family member genes. Though the exactrepertoire of ALDH family member gene products capable of Aldefluor™processing remains unclear, ALDH1 is believed to be a substrate forAldefluor™ and ALDH1 mRNA and protein levels correlate with resistanceto CPA (Magni M, Shammah S, Schiro R, Mellado W, Dalla-Favera R, GianniA M., Blood (1996) 87:1097-1103; Moreb J S, Turner C, Sreerama L, ZucaliJ R, Sladek N E, Schweder M., Leuk. Lymphoma (1995) 20:77-84; Quash G,Fournet G, Chantepie J, et al., Biochem. Pharmacol. (2002) 64:1279-1292;Sladek N E, Kollander R, Sreerama L, Kiang D T. Cancer Chemother.Pharmacol. (2002) 49:309-321; Yang X W, Wang W, Fu J X, et al., ZhongguoShi Yan Xue Ye Xue Za Zhi. (2002) 10:205-208). Procedurally,ALDH-specific increases in Aldefluor™ fluorescence observed by FACS aredetermined against a control containing a competitive inhibitor of ALDH;diethylaminobenzaldehyde (DEAB). Recent studies involving DEAB suggestan important role for ALDH enzymes in determining HSC fate, andspecifically that HSC differentiation requires the retinoic acidsgenerated by intracellular ALDH (Chute J P, Muramoto G G, Whitesides J,et al., Proc. Natl. Acad. Sci. USA. (2006) 103:11707-12.

Additional solid tumor stem cells cancer markers can be identified, forexample, using the methods described in Example 2 below.

The invention for the first time identifies colon cancer stem cellmarkers that are upregulated in colon cancer stem cells compared tonontumorigenic colon tumor cells. These markers can be used to provide adiagnosis, prognosis, and/or select a therapy based on theidentification and quantification of colon cancer stem cells in a tumoras well as to monitor a diagnosis, prognosis, and/or therapy over time.If it is known that a patient has a tumor that contains a significantnumber of colon cancer stem cells, a more aggressive approach to therapycan be warranted than in tumors that contain a smaller number of coloncancer stem cells. For example, in patients where there is no evidenceof disease in lymph nodes (node-negative patients), a decision must bemade regarding whether to administer chemotherapy (adjuvant therapy)following surgical removal of the tumor. While some patients are likelyto benefit from such treatment, it has significant side effects and canpreferably be avoided by patients with tumors that contain few cancerstem cells. Presently it is difficult or impossible to predict whichpatients would benefit. Detecting and quantifying the number of cancerstem cell in a patient can help in this decision. Furthermore, detectingthe colon cancer stem cell markers of the present invention can provideinformation related to tumor progression. It is well known that astumors progress, their phenotypic characteristics may change. Theinvention thus contemplates the possibility that colon tumors may evolvefrom containing a small number of colon cancer stem cells to containinga larger number (or vice versa) either in response to therapy or inresponse to lack of therapy. Thus detection of colon cancer stem cellmarkers can be used to detect such progression and alter therapyaccordingly.

It is well known in the art that some tumors respond to certaintherapies while others do not. At present there is very littleinformation that may be used to determine, prior to treatment, thelikelihood that a specific tumor will respond to a given therapeuticagent. Many compounds have been tested for anti-tumor activity andappear to be effective in only a small percentage of tumors. Due to thecurrent inability to predict which tumors will respond to a given agent,these compounds have not been developed into marketed therapeutics. Thisproblem reflects the fact that current methods of classifying tumors arelimited. However, the present invention offers the possibility ofcharacterizing tumors based on the presence of cancer stem cell markersand thus increasing the likelihood of response to a given agent. Tumorsample archives containing tissue samples obtained from patients thathave undergone therapy with various agents are available along withinformation regarding the results of such therapy. In general sucharchives consist of tumor samples embedded in paraffin blocks. Thesetumor samples can be analyzed for their expression of colon cancer stemcell marker polypeptides of the present invention. For example,immunohistochemistry can be performed using antibodies that bind to thepolypeptides. Alternatively these tumor samples can be analyzed by theirexpression of polynucleotides of a colon cancer stem cell marker of thepresent invention. For example, RNA can be extracted from the tumorsample and RT-PCR used to quantitatively amplify colon cancer stem cellmarker mRNAs. It is then possible to correlate the expression of coloncancer stem cell markers with the response of the tumor to therapy,thereby identifying particular compounds that show a superior efficacyagainst colon cancer stem cells. Once such compounds are identified itwill be possible to select patients for additional clinical trials usingthese compounds. Such clinical trials, performed on a selected group ofpatients, are more likely to demonstrate efficacy. The reagents providedherein, therefore, are valuable both for retrospective and prospectivetrials.

In certain embodiments of the present invention, colon cancer stem cellmarkers can be used experimentally to test and assess lead compoundsincluding, for example, small molecules, siRNAs, and antibodies for thetreatment of cancer. For example tumor cells from a patient can bescreened for colon cancer stem cells and then transplanted into thexenograft model described herein and the effect of test compounds, suchas for example antibodies against one or more of the colon cancer stemcell markers described herein, tested for effects on tumor growth andsurvival. Furthermore the number of colon cancer stem cells can bedetermined following treatment to assess the effectiveness of thetherapy on targeting cancer stem cells and used to guide a futuretreatment regimen.

Detection of Solid Tumor Stem Cell Cancer Markers

In some embodiments, the present invention provides methods fordetection of expression of stem cell cancer markers (e.g., breast cancerstem cell cancer markers). In some embodiments, expression is measureddirectly (e.g., at the RNA or protein level). In some embodiments,expression is detected in tissue samples (e.g., biopsy tissue). In otherembodiments, expression is detected in bodily fluids (e.g., includingbut not limited to, plasma, serum, whole blood, mucus, and urine). Thepresent invention further provides panels and kits for the detection ofmarkers. In some embodiments, the presence of a stem cell cancer markeris used to provide a prognosis to a subject. The information provided isalso used to direct the course of treatment. For example, if a subjectis found to have a marker indicative of a solid tumor stem cell (see,e.g. Tables 4-9), additional therapies (e.g., hormonal or radiationtherapies) can be started at an earlier point when they are more likelyto be effective (e.g., before metastasis). In addition, if a subject isfound to have a tumor that is not responsive to hormonal therapy, theexpense and inconvenience of such therapies can be avoided.

The present invention is not limited to the markers described above. Anysuitable marker that correlates with cancer or the progression of cancercan be utilized. Additional markers are also contemplated to be withinthe scope of the present invention. Any suitable method can be utilizedto identify and characterize cancer markers suitable for use in themethods of the present invention, including but not limited to, thosedescribed in illustrative Example 4 below. For example, in someembodiments, markers identified as being up or down-regulated in solidtumor stem cells using the gene expression microarray methods of thepresent invention are further characterized using tissue microarray,immunohistochemistry, Northern blot analysis, siRNA or antisense RNAinhibition, mutation analysis, investigation of expression with clinicaloutcome, as well as other methods disclosed herein.

In some embodiments, the present invention provides a panel for theanalysis of a plurality of markers. The panel allows for thesimultaneous analysis of multiple markers correlating withcarcinogenesis and/or metastasis. Depending on the subject, panels canbe analyzed alone or in combination in order to provide the bestpossible diagnosis and prognosis. Markers for inclusion on a panel areselected by screening for their predictive value using any suitablemethod, including but not limited to, those described in theillustrative examples below.

1. Detection of RNA

In some embodiments, detection of solid tumor stem cell cancer markers(e.g., including but not limited to, those disclosed in Tables 4-9) aredetected by measuring the expression of corresponding mRNA in a tissuesample (e.g., breast cancer tissue). mRNA expression can be measured byany suitable method, including but not limited to, those disclosedbelow.

In some embodiments, RNA is detection by Northern blot analysis.Northern blot analysis involves the separation of RNA and hybridizationof a complementary labeled probe.

In still further embodiments, RNA (or corresponding cDNA) is detected byhybridization to an oligonucleotide probe). A variety of hybridizationassays using a variety of technologies for hybridization and detectionare available. For example, in some embodiments, TaqMan assay (PEBiosystems, Foster City, Calif.; See e.g., U.S. Pat. Nos. 5,962,233 and5,538,848, each of which is herein incorporated by reference) isutilized. The assay is performed during a PCR reaction. The TaqMan assayexploits the 5′-3′ exonuclease activity of the AMPLITAQ GOLD DNApolymerase. A probe consisting of an oligonucleotide with a 5′-reporterdye (e.g., a fluorescent dye) and a 3′-quencher dye is included in thePCR reaction. During PCR, if the probe is bound to its target, the 5′-3′nucleolytic activity of the AMPLITAQ GOLD polymerase cleaves the probebetween the reporter and the quencher dye. The separation of thereporter dye from the quencher dye results in an increase offluorescence. The signal accumulates with each cycle of PCR and can bemonitored with a fluorimeter.

In yet other embodiments, reverse-transcriptase PCR (RT-PCR) is used todetect the expression of RNA. In RT-PCR, RNA is enzymatically convertedto complementary DNA or “cDNA” using a reverse transcriptase enzyme. ThecDNA is then used as a template for a PCR reaction. PCR products can bedetected by any suitable method, including but not limited to, gelelectrophoresis and staining with a DNA specific stain or hybridizationto a labeled probe. In some embodiments, the quantitative reversetranscriptase PCR with standardized mixtures of competitive templatesmethod described in U.S. Pat. Nos. 5,639,606, 5,643,765, and 5,876,978(each of which is herein incorporated by reference) is utilized.

2. Detection of Protein

In other embodiments, gene expression of stem cell cancer markers isdetected by measuring the expression of the corresponding protein orpolypeptide. Protein expression can be detected by any suitable method.In some embodiments, proteins are detected by immunohistochemistry. Inother embodiments, proteins are detected by their binding to an antibodyraised against the protein. The generation of antibodies is describedbelow.

Antibody binding is detected by techniques known in the art (e.g.,radioimmunoassay, ELISA (enzyme-linked immunosorbant assay), “sandwich”immunoassays, immunoradiometric assays, gel diffusion precipitationreactions, immunodiffusion assays, in situ immunoassays (e.g., usingcolloidal gold, enzyme or radioisotope labels, for example), Westernblots, precipitation reactions, agglutination assays (e.g., gelagglutination assays, hemagglutination assays, etc.), complementfixation assays, immunofluorescence assays, protein A assays, andimmunoelectrophoresis assays, etc.

In one embodiment, antibody binding is detected by detecting a label onthe primary antibody. In another embodiment, the primary antibody isdetected by detecting binding of a secondary antibody or reagent to theprimary antibody. In a further embodiment, the secondary antibody islabeled. Many methods are known in the art for detecting binding in animmunoassay and are within the scope of the present invention.

In some embodiments, an automated detection assay is utilized. Methodsfor the automation of immunoassays include those described in U.S. Pat.Nos. 5,885,530, 4,981,785, 6,159,750, and 5,358,691, each of which isherein incorporated by reference. In some embodiments, the analysis andpresentation of results is also automated. For example, in someembodiments, software that generates a prognosis based on the presenceor absence of a series of proteins corresponding to cancer markers isutilized.

In other embodiments, the immunoassay described in U.S. Pat. Nos.5,599,677 and 5,672,480; each of which is herein incorporated byreference.

3. cDNA Microarray Technology

cDNA microarrays consist of multiple (usually thousands) of differentcDNAs spotted (usually using a robotic spotting device) onto knownlocations on a solid support, such as a glass microscope slide. ThecDNAs are typically obtained by PCR amplification of plasmid libraryinserts using primers complementary to the vector backbone portion ofthe plasmid or to the gene itself for genes where sequence is known. PCRproducts suitable for production of microarrays are typically between0.5 and 2.5 kB in length Full length cDNAs, expressed sequence tags(ESTs), or randomly chosen cDNAs from any library of interest can bechosen. ESTs are partially sequenced cDNAs as described, for example, inHillier, et al., 1996, 6:807-828. Although some ESTs correspond to knowngenes, frequently very little or no information regarding any particularEST is available except for a small amount of 3′ and/or 5′ sequence and,possibly, the tissue of origin of the mRNA from which the EST wasderived. As will be appreciated by one of ordinary skill in the art, ingeneral the cDNAs contain sufficient sequence information to uniquelyidentify a gene within the human genome. Furthermore, in general thecDNAs are of sufficient length to hybridize, selectively, specificallyor uniquely, to cDNA obtained from mRNA derived from a single gene underthe hybridization conditions of the experiment.

In a typical microarray experiment, a microarray is hybridized withdifferentially labeled RNA, DNA, or cDNA populations derived from twodifferent samples. Most commonly RNA (either total RNA or poly A+ RNA)is isolated from cells or tissues of interest and is reverse transcribedto yield cDNA. Labeling is usually performed during reversetranscription by incorporating a labeled nucleotide in the reactionmixture. Although various labels can be used, most commonly thenucleotide is conjugated with the fluorescent dyes Cy3 or Cy5. Forexample, Cy5-dUTP and Cy3-dUTP can be used. cDNA derived from one sample(representing, for example, a particular cell type, tissue type orgrowth condition) is labeled with one fluorophore while cDNA derivedfrom a second sample (representing, for example, a different cell type,tissue type, or growth condition) is labeled with the secondfluorophore. Similar amounts of labeled material from the two samplesare cohybridized to the microarray. In the case of a microarrayexperiment in which the samples are labeled with Cy5 (which fluorescesred) and Cy3 (which fluoresces green), the primary data (obtained byscanning the microarray using a detector capable of quantitativelydetecting fluorescence intensity) are ratios of fluorescence intensity(red/green, R/G). These ratios represent the relative concentrations ofcDNA molecules that hybridized to the cDNAs represented on themicroarray and thus reflect the relative expression levels of the mRNAcorresponding to each cDNA/gene represented on the microarray.

Each microarray experiment can provide tens of thousands of data points,each representing the relative expression of a particular gene in thetwo samples. Appropriate organization and analysis of the data is of keyimportance, and various computer programs that incorporate standardstatistical tools have been developed to facilitate data analysis. Onebasis for organizing gene expression data is to group genes with similarexpression patterns together into clusters. A method for performinghierarchical cluster analysis and display of data derived frommicroarray experiments is described in Eisen et al., 1998, PNAS95:14863-14868. As described therein, clustering can be combined with agraphical representation of the primary data in which each data point isrepresented with a color that quantitatively and qualitativelyrepresents that data point. By converting the data from a large table ofnumbers into a visual format, this process facilitates an intuitiveanalysis of the data. Additional information and details regarding themathematical tools and/or the clustering approach itself can be found,for example, in Sokal & Sneath, Principles of numerical taxonomy, xvi,359, W. H. Freeman, San Francisco, 1963; Hartigan, Clusteringalgorithms, xiii, 351, Wiley, New York, 1975; Paull et al., 1989, J.Natl. Cancer Inst. 81:1088-92; Weinstein et al. 1992, Science258:447-51; van Osdol et al., 1994, J. Natl. Cancer Inst. 86:1853-9; andWeinstein et al., 1997, Science, 275:343-9.

Further details of the experimental methods used in the presentinvention are found in the Examples. Additional information describingmethods for fabricating and using microarrays is found in U.S. Pat. No.5,807,522, which is herein incorporated by reference. Instructions forconstructing microarray hardware (e.g., arrayers and scanners) usingcommercially available parts can be found athttp://cmgm.stanford.edu/pbr-own/ and in Cheung et al., 1999, Nat.Genet. Supplement 21:15-19, which are herein incorporated by reference.Additional discussions of microarray technology and protocols forpreparing samples and performing microrarray experiments are found in,for example, DNA arrays for analysis of gene expression, MethodsEnzymol, 303:179-205, 1999; Fluorescence-based expression monitoringusing microarrays, Methods Enzymol, 306: 3-18, 1999; and M. Schena(ed.), DNA Microarrays: A Practical Approach, Oxford University Press,Oxford, UK, 1999. Descriptions of how to use an arrayer and theassociated software are found athttp://cmgm.stanford.edu/pbrown/mguide/a-rrayerHTML/ArrayerDocs.html,which is herein incorporated by reference.

4. Data Analysis

In some embodiments, a computer-based analysis program is used totranslate the raw data generated by the detection assay (e.g., thepresence, absence, or amount of a given marker or markers) into data ofpredictive value for a clinician. The clinician can access thepredictive data using any suitable means. Thus, in some embodiments, thepresent invention provides the further benefit that the clinician, whois not likely to be trained in genetics or molecular biology, need notunderstand the raw data. The data is presented directly to the clinicianin its most useful form. The clinician is then able to immediatelyutilize the information in order to optimize the care of the subject.

The present invention contemplates any method capable of receiving,processing, and transmitting the information to and from laboratoriesconducting the assays, information provides, medical personal, andsubjects. For example, in some embodiments of the present invention, asample (e.g., a biopsy or a serum or urine sample) is obtained from asubject and submitted to a profiling service (e.g., clinical lab at amedical facility, genomic profiling business, etc.), located in any partof the world (e.g., in a country different than the country where thesubject resides or where the information is ultimately used) to generateraw data. Where the sample comprises a tissue or other biologicalsample, the subject can visit a medical center to have the sampleobtained and sent to the profiling center, or subjects can collect thesample themselves and directly send it to a profiling center. Where thesample comprises previously determined biological information, theinformation can be directly sent to the profiling service by the subject(e.g., an information card containing the information can be scanned bya computer and the data transmitted to a computer of the profilingcenter using an electronic communication system). Once received by theprofiling service, the sample is processed and a profile is produced(e.g., expression data), specific for the diagnostic or prognosticinformation desired for the subject.

The profile data is then prepared in a format suitable forinterpretation by a treating clinician. For example, rather thanproviding raw expression data (e.g. examining a number of the markersdescribed in Tables 4-9), the prepared format can represent a diagnosisor risk assessment for the subject, along with recommendations forparticular treatment options. The data can be displayed to the clinicianby any suitable method. For example, in some embodiments, the profilingservice generates a report that can be printed for the clinician (e.g.,at the point of care) or displayed to the clinician on a computermonitor.

In some embodiments, the information is first analyzed at the point ofcare or at a regional facility. The raw data is then sent to a centralprocessing facility for further analysis and/or to convert the raw datato information useful for a clinician or patient. The central processingfacility provides the advantage of privacy (all data is stored in acentral facility with uniform security protocols), speed, and uniformityof data analysis. The central processing facility can then control thefate of the data following treatment of the subject. For example, usingan electronic communication system, the central facility can providedata to the clinician, the subject, or researchers.

In some embodiments, the subject is able to directly access the datausing the electronic communication system. The subject can chose furtherintervention or counseling based on the results. In some embodiments,the data is used for research use. For example, the data can be used tofurther optimize the inclusion or elimination of markers as usefulindicators of a particular condition or stage of disease.

5. Kits

In yet other embodiments, the present invention provides kits for thedetection and characterization of cancer (e.g. for detecting one or moreof the markers shown in Tables 4-9, or for modulating the activity of apeptide expressed by one or more of markers shown in Tables 4-9). Insome embodiments, the kits contain antibodies specific for a cancermarker, in addition to detection reagents and buffers. In otherembodiments, the kits contain reagents specific for the detection ofmRNA or cDNA (e.g., oligonucleotide probes or primers). In someembodiments, the kits contain all of the components necessary and/orsufficient to perform a detection assay, including all controls,directions for performing assays, and any necessary software foranalysis and presentation of results.

Another embodiment of the present invention comprises a kit to test forthe presence of the polynucleotides or proteins, e.g. in a tissue sampleor in a body fluid, of a solid tumor stem cell gene signature, such asthe alpha-catenin signature. The kit can comprise for example, anantibody for detection of a polypeptide or a probe for detection of apolynucleotide. In addition, the kit can comprise a reference or controlsample; instructions for processing samples, performing the test andinterpreting the results; and buffers and other reagents necessary forperforming the test. In certain embodiments the kit comprises a panel ofantibodies for detecting expression of one or more of the proteinsencoded by the genes of the alpha-catenin signature. In otherembodiments the kit comprises pairs of primers for detecting expressionof one or more of the genes of the solid tumor stem cell gene signature.In other embodiments the kit comprises a cDNA or oligonucleotide arrayfor detecting expression of one or more of the genes of the solid tumorstem cell gene signature.

6. In Vivo Imaging

In some embodiments, in vivo imaging techniques are used to visualizethe expression of cancer markers in an animal (e.g., a human ornon-human mammal). For example, in some embodiments, cancer marker mRNAor protein is labeled using a labeled antibody specific for the cancermarker. A specifically bound and labeled antibody can be detected in anindividual using an in vivo imaging method, including, but not limitedto, radionuclide imaging, positron emission tomography, computerizedaxial tomography, X-ray or magnetic resonance imaging method,fluorescence detection, and chemiluminescent detection. Methods forgenerating antibodies to the cancer markers of the present invention aredescribed below.

The in vivo imaging methods of the present invention are useful in thediagnosis of cancers that express the solid tumor stem cell cancermarkers of the present invention (e.g., in breast cancer). In vivoimaging is used to visualize the presence of a marker indicative of thecancer. Such techniques allow for diagnosis without the use of anunpleasant biopsy. The in vivo imaging methods of the present inventionare also useful for providing prognoses to cancer patients. For example,the presence of a marker indicative of cancer stem cells can bedetected. The in vivo imaging methods of the present invention canfurther be used to detect metastatic cancers in other parts of the body.

In some embodiments, reagents (e.g., antibodies) specific for the cancermarkers of the present invention are fluorescently labeled. The labeledantibodies are introduced into a subject (e.g., orally or parenterally).Fluorescently labeled antibodies are detected using any suitable method(e.g., using the apparatus described in U.S. Pat. No. 6,198,107, hereinincorporated by reference).

In other embodiments, antibodies are radioactively labeled. The use ofantibodies for in vivo diagnosis is well known in the art. Sumerdon etal., (Nucl. Med. Biol 17:247-254 [1990] have described an optimizedantibody-chelator for the radioimmunoscintographic imaging of tumorsusing Indium-111 as the label. Griffin et al., (J Clin One 9:631-640[1991]) have described the use of this agent in detecting tumors inpatients suspected of having recurrent colorectal cancer. The use ofsimilar agents with paramagnetic ions as labels for magnetic resonanceimaging is known in the art (Lauffer, Magnetic Resonance in Medicine22:339-342 [1991]). The label used will depend on the imaging modalitychosen. Radioactive labels such as Indium-111, Technetium-99m, orIodine-131 can be used for planar scans or single photon emissioncomputed tomography (SPECT). Positron emitting labels such asFluorine-19 can also be used for positron emission tomography (PET). ForMRI, paramagnetic ions such as Gadolinium (III) or Manganese (II) can beused.

Radioactive metals with half-lives ranging from 1 hour to 3.5 days areavailable for conjugation to antibodies, such as scandium-47 (3.5 days)gallium-67 (2.8 days), gallium-68 (68 minutes), technetiium-99m (6hours), and indium-111 (3.2 days), of which gallium-67, technetium-99m,and indium-111 are preferable for gamma camera imaging, gallium-68 ispreferable for positron emission tomography.

A useful method of labeling antibodies with such radiometals is by meansof a bifunctional chelating agent, such as diethylenetriaminepentaaceticacid (DTPA), as described, for example, by Khaw et al. (Science 209:295[1980]) for In-111 and Tc-99m, and by Scheinberg et al. (Science215:1511 [1982]). Other chelating agents can also be used, but the1-(p-carboxymethoxybenzyl)EDTA and the carboxycarbonic anhydride of DTPAare advantageous because their use permits conjugation without affectingthe antibody's immunoreactivity substantially.

Another method for coupling DPTA to proteins is by use of the cyclicanhydride of DTPA, as described by Hnatowich et al. (Int. J. Appl.Radiat. Isot. 33:327 [1982]) for labeling of albumin with In-111, butwhich can be adapted for labeling of antibodies. A suitable method oflabeling antibodies with Tc-99m which does not use chelation with DPTAis the pretinning method of Crockford et al., (U.S. Pat. No. 4,323,546,herein incorporated by reference).

A method of labeling immunoglobulins with Tc-99m is that described byWong et al. (Int. J. Appl. Radiat. Isot., 29:251 [1978]) for plasmaprotein, and recently applied successfully by Wong et al. (J. Nucl.Med., 23:229 [1981]) for labeling antibodies.

In the case of the radiometals conjugated to the specific antibody, itis likewise desirable to introduce as high a proportion of theradiolabel as possible into the antibody molecule without destroying itsimmunospecificity. A further improvement can be achieved by effectingradiolabeling in the presence of the specific stem cell cancer marker ofthe present invention, to insure that the antigen binding site on theantibody will be protected.

In still further embodiments, in vivo biophotonic imaging (Xenogen,Almeda, Calif.) is utilized for in vivo imaging. This real-time in vivoimaging utilizes luciferase. The luciferase gene is incorporated intocells, microorganisms, and animals (e.g., as a fusion protein with acancer marker of the present invention). When active, it leads to areaction that emits light. A CCD camera and software is used to capturethe image and analyze it.

Antibodies and Antibody Fragments

The present invention provides isolated antibodies against a cancer stemcell marker. The antibody, or antibody fragment, can be any monoclonalor polyclonal antibody that specifically recognizes the described coloncancer stem cell marker. In some embodiments, the present inventionprovides monoclonal antibodies, or fragments thereof, that specificallybind to a colon cancer stem cell marker polypeptide described herein. Insome embodiments, the monoclonal antibodies, or fragments thereof, arechimeric or humanized antibodies that specifically bind to theextracellular domain of a colon cancer stem cell marker polypeptidedescribed herein. In other embodiments, the monoclonal antibodies, orfragments thereof, are human antibodies that specifically bind to theextracellular domain of a colon cancer stem cell marker polypeptidedescribed herein.

The antibodies against a cancer stem cell marker find use in theexperimental, diagnostic and therapeutic methods described herein. Incertain embodiments, the antibodies of the present invention are used todetect the expression of a colon cancer stem cell marker protein inbiological samples such as, for example, a patient tissue biopsy,pleural effusion, or blood sample. Tissue biopsies can be sectioned andprotein detected using, for example, immunofluorescence orimmunohistochemistry. Alternatively, individual cells from a sample areisolated, and protein expression detected on fixed or live cells by FACSanalysis. Furthermore, the antibodies can be used on protein arrays todetect expression of a colon cancer stem cell marker, for example, ontumor cells, in cell lysates, or in other protein samples. In otherembodiments, the antibodies of the present invention are used to inhibitthe growth of tumor cells by contacting the antibodies with tumor cellseither in vitro cell based assays or in vivo animal models. In stillother embodiments, the antibodies are used to treat cancer in a humanpatient by administering a therapeutically effective amount of anantibody against a colon cancer stem cell marker.

Polyclonal antibodies can be prepared by any known method. Polyclonalantibodies can be raised by immunizing an animal (e.g. a rabbit, rat,mouse, donkey, etc) by multiple subcutaneous or intraperitonealinjections of the relevant antigen (a purified peptide fragment,full-length recombinant protein, fusion protein, etc) optionallyconjugated to keyhole limpet hemocyanin (KLH), serum albumin, etc.diluted in sterile saline and combined with an adjuvant (e.g. Completeor Incomplete Freund's Adjuvant) to form a stable emulsion. Thepolyclonal antibody is then recovered from blood, ascites and the like,of an animal so immunized. Collected blood is clotted, and the serumdecanted, clarified by centrifugation, and assayed for antibody titer.The polyclonal antibodies can be purified from serum or ascitesaccording to standard methods in the art including affinitychromatography, ion-exchange chromatography, gel electrophoresis,dialysis, etc.

Monoclonal antibodies can be prepared using hybridoma methods, such asthose described by Kohler and Milstein (1975) Nature 256:495. Using thehybridoma method, a mouse, hamster, or other appropriate host animal, isimmunized as described above to elicit the production by lymphocytes ofantibodies that will specifically bind to an immunizing antigen.Alternatively, lymphocytes can be immunized in vitro. Followingimmunization, the lymphocytes are isolated and fused with a suitablemyeloma cell line using, for example, polyethylene glycol, to formhybridoma cells that can then be selected away from unfused lymphocytesand myeloma cells. Hybridomas that produce monoclonal antibodiesdirected specifically against a chosen antigen as determined byimmunoprecipitation, immunoblotting, or by an in vitro binding assaysuch as radioimmunoassay (RIA) or enzyme-linked immunosorbent assay(ELISA) can then be propagated either in vitro culture using standardmethods (Goding, Monoclonal Antibodies: Principles and Practice,Academic Press, 1986) or in vivo as ascites tumors in an animal. Themonoclonal antibodies can then be purified from the culture medium orascites fluid as described for polyclonal antibodies above.

Alternatively monoclonal antibodies can also be made using recombinantDNA methods as described in U.S. Pat. No. 4,816,567. The polynucleotidesencoding a monoclonal antibody are isolated, such as from mature B-cellsor hybridoma cell, such as by RT-PCR using oligonucleotide primers thatspecifically amplify the genes encoding the heavy and light chains ofthe antibody, and their sequence is determined using conventionalprocedures. The isolated polynucleotides encoding the heavy and lightchains are then cloned into suitable expression vectors, which whentransfected into host cells such as E. coli cells, simian COS cells,Chinese hamster ovary (CHO) cells, or myeloma cells that do nototherwise produce immunoglobulin protein, monoclonal antibodies aregenerated by the host cells. Also, recombinant monoclonal antibodies orfragments thereof of the desired species can be isolated from phagedisplay libraries as described (McCafferty et al., 1990, Nature,348:552-554; Clackson et al., 1991, Nature, 352:624-628; and Marks etal., 1991, J. Mol. Biol., 222:581-597).

The polynucleotide(s) encoding a monoclonal antibody can further bemodified in a number of different manners using recombinant DNAtechnology to generate alternative antibodies. In one embodiment, theconstant domains of the light and heavy chains of, for example, a mousemonoclonal antibody can be substituted 1) for those regions of, forexample, a human antibody to generate a chimeric antibody or 2) for anon-immunoglobulin polypeptide to generate a fusion antibody. In otherembodiments, the constant regions are truncated or removed to generatethe desired antibody fragment of a monoclonal antibody. Furthermore,site-directed or high-density mutagenesis of the variable region can beused to optimize specificity, affinity, etc. of a monoclonal antibody.

In some embodiments, of the present invention the monoclonal antibodyagainst a colon cancer stem cell marker is a humanized antibody.Humanized antibodies are antibodies that contain minimal sequences fromnon-human (e.g murine) antibodies within the variable regions. Suchantibodies are used therapeutically to reduce antigenicity and HAMA(human anti-mouse antibody) responses when administered to a humansubject. In practice, humanized antibodies are typically humanantibodies with minimum to no non-human sequences. A human antibody isan antibody produced by a human or an antibody having an amino acidsequence corresponding to an antibody produced by a human.

Humanized antibodies can be produced using various techniques known inthe art. An antibody can be humanized by substituting the CDR of a humanantibody with that of a non-human antibody (e.g. mouse, rat, rabbit,hamster, etc.) having the desired specificity, affinity, and capability(Jones et al., 1986, Nature, 321:522-525; Riechmann et al., 1988,Nature, 332:323-327; Verhoeyen et al., 1988, Science, 239:1534-1536).The humanized antibody can be further modified by the substitution ofadditional residue either in the Fv framework region and/or within thereplaced non-human residues to refine and optimize antibody specificity,affinity, and/or capability.

Human antibodies can be directly prepared using various techniques knownin the art. Immortalized human B lymphocytes immunized in vitro orisolated from an immunized individual that produce an antibody directedagainst a target antigen can be generated (See, for example, Cole etal., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p. 77(1985); Boerner et al., 1991, J. Immunol., 147 (1):86-95; and U.S. Pat.No. 5,750,373). Also, the human antibody can be selected from a phagelibrary, where that phage library expresses human antibodies (Vaughan etal., 1996, Nature Biotechnology, 14:309-314; Sheets et al., 1998, PNAS,95:6157-6162; Hoogenboom and Winter, 1991, J. Mol. Biol., 227:381; Markset al., 1991, J. Mol. Biol., 222:581). Humanized antibodies can also bemade in transgenic mice containing human immunoglobulin loci that arecapable upon immunization of producing the full repertoire of humanantibodies in the absence of endogenous immunoglobulin production. Thisapproach is described in U.S. Pat. Nos. 5,545,807; 5,545,806; 5,569,825;5,625,126; 5,633,425; and 5,661,016.

This invention also encompasses bispecific antibodies that specificallyrecognize a colon cancer stem cell marker. Bispecific antibodies areantibodies that are capable of specifically recognizing and binding atleast two different epitopes. The different epitopes can either bewithin the same molecule (e.g. the same colon cancer stem cell markerpolypeptide) or on different molecules such that both, for example, theantibodies can specifically recognize and bind a colon cancer stem cellmarker as well as, for example, 1) an effector molecule on a leukocytesuch as a T-cell receptor (e.g. CD3) or Fc receptor (e.g. CD64, CD32, orCD16) or 2) a cytotoxic agent as described in detail below. Bispecificantibodies can be intact antibodies or antibody fragments. Techniquesfor making bispecific antibodies are common in the art (Millstein etal., 1983, Nature 305:537-539; Brennan et al., 1985, Science 229:81;Suresh et al, 1986, Methods in Enzymol. 121:120; Traunecker et al.,1991, EMBO J. 10:3655-3659; Shalaby et al., 1992, J. Exp. Med.175:217-225; Kostelny et al., 1992, J. Immunol. 148:1547-1553; Gruber etal., 1994, J. Immunol. 152:5368; and U.S. Pat. No. 5,731,168).

In certain embodiments of the invention, it may be desirable to use anantibody fragment, rather than an intact antibody, to increase tumorpenetration, for example. Various techniques are known for theproduction of antibody fragments. Traditionally, these fragments arederived via proteolytic digestion of intact antibodies (for exampleMorimoto et al., 1993, Journal of Biochemical and Biophysical Methods24:107-117 and Brennan et al., 1985, Science, 229:81). However, thesefragments are now typically produced directly by recombinant host cellsas described above. Thus Fab, Fv, and scFv antibody fragments can all beexpressed in and secreted from E. coli or other host cells, thusallowing the production of large amounts of these fragments.Alternatively, such antibody fragments can be isolated from the antibodyphage libraries discussed above. The antibody fragment can also belinear antibodies as described in U.S. Pat. No. 5,641,870, for example,and can be monospecific or bispecific. Other techniques for theproduction of antibody fragments will be apparent to the skilledpractitioner.

It may further be desirable, especially in the case of antibodyfragments, to modify an antibody in order to increase its serumhalf-life. This can be achieved, for example, by incorporation of asalvage receptor binding epitope into the antibody fragment by mutationof the appropriate region in the antibody fragment or by incorporatingthe epitope into a peptide tag that is then fused to the antibodyfragment at either end or in the middle (e.g., by DNA or peptidesynthesis).

The present invention further embraces variants and equivalents whichare substantially homologous to the chimeric, humanized and humanantibodies, or antibody fragments thereof, set forth herein. These cancontain, for example, conservative substitution mutations, i.e. thesubstitution of one or more amino acids by similar amino acids. Forexample, conservative substitution refers to the substitution of anamino acid with another within the same general class such as, forexample, one acidic amino acid with another acidic amino acid, one basicamino acid with another basic amino acid or one neutral amino acid byanother neutral amino acid. What is intended by a conservative aminoacid substitution is well known in the art.

The invention also pertains to immunoconjugates comprising an antibodyconjugated to a cytotoxic agent. Cytotoxic agents includechemotherapeutic agents, growth inhibitory agents, toxins (e.g., anenzymatically active toxin of bacterial, fungal, plant, or animalorigin, or fragments thereof), radioactive isotopes (i.e., aradioconjugate), etc. Chemotherapeutic agents useful in the generationof such immunoconjugates include, for example, methotrexate, adriamicin,doxorubicin, melphalan, mitomycin C, chlorambucil, daunorubicin or otherintercalating agents. Enzymatically active toxins and fragments thereofthat can be used include diphtheria A chain, nonbinding active fragmentsof diphtheria toxin, exotoxin A chain, ricin A chain, abrin A chain,modeccin A chain, alpha-sarcin, Aleurites fordii proteins, dianthinproteins, Phytolaca americana proteins (PAPI, PAPII, and PAP-S),momordica charantia inhibitor, curcin, crotin, sapaonaria officinalisinhibitor, gelonin, mitogellin, restrictocin, phenomycin, enomycin, andthe tricothecenes. A variety of radionuclides are available for theproduction of radioconjugated antibodies including ²¹²Bi, ¹³¹I, ¹³¹In,⁹⁰Y, and ¹⁸⁶Re. Conjugates of the antibody and cytotoxic agent are madeusing a variety of bifunctional protein-coupling agents such asN-succinimidyl-3-(2-pyridyldithiol) propionate (SPDP), iminothiolane(IT), bifunctional derivatives of imidoesters (such as dimethyladipimidate HCL), active esters (such as disuccinimidyl suberate),aldehydes (such as glutareldehyde), bis-azido compounds (such asbis(p-azidobenzoyl) hexanediamine), bis-diazonium derivatives (such asbis-(p-diazoniumbenzoyl)-ethylenediamine), diisocyanates (such astolyene 2,6-diisocyanate), and bis-active fluorine compounds (such as1,5-difluoro-2,4-dinitrobenzene). Conjugates of an antibody and one ormore small molecule toxins, such as a calicheamicin, maytansinoids, atrichothene, and CC1065, and the derivatives of these toxins that havetoxin activity, can also be used.

In some embodiments the antibody of the invention contains human Fcregions that are modified to enhance effector function, for example,antigen-dependent cell-mediated cyotoxicity (ADCC) and/or complementdependent cytotoxicity (CDC). This can be achieved by introducing one ormore amino acid substitutions in an Fc region of the antibody. Forexample, cysteine residue(s) can be introduced in the Fc region to allowinterchain disulfide bond formation in this region to improvecomplement-mediated cell killing and antibody-dependent cellularcytotoxicity (ADCC) (Caron et al., 1992, J. Exp Med. 176:1191-1195;Shopes, 1992, Immunol. 148:2918-2922). Homodimeric antibodies withenhanced anti-tumor activity can also be prepared usingheterobifunctional cross-linkers as described in Wolff et al., 1993,Cancer Research 53:2560-2565. Alternatively, an antibody can beengineered which has dual Fc regions (Stevenson et al., 1989,Anti-Cancer Drug Design 3:219-230).

Drug Screening

In some embodiments, the present invention provides drug screeningassays (e.g., to screen for anticancer drugs). The screening methods ofthe present invention utilize stem cell cancer markers identified usingthe methods of the present invention (e.g., including but not limitedto, the stem cell cancer markers shown in Tables 4-9). For example, insome embodiments, the present invention provides methods of screeningfor compound that alter (e.g., increase or decrease) the expression ofstem cell cancer marker genes. In some embodiments, candidate compoundsare antisense agents or siRNA agents (e.g., oligonucleotides) directedagainst cancer markers. In other embodiments, candidate compounds areantibodies that specifically bind to a stem cell cancer marker of thepresent invention. In certain embodiments, libraries of compounds ofsmall molecules are screened using the methods described herein.

In one screening method, candidate compounds are evaluated for theirability to alter stem cell cancer marker expression by contacting acompound with a cell expressing a stem cell cancer marker and thenassaying for the effect of the candidate compounds on expression. Insome embodiments, the effect of candidate compounds on expression of acancer marker gene is assayed by detecting the level of cancer markermRNA expressed by the cell. mRNA expression can be detected by anysuitable method. In other embodiments, the effect of candidate compoundson expression of cancer marker genes is assayed by measuring the levelof polypeptide encoded by the cancer markers. The level of polypeptideexpressed can be measured using any suitable method, including but notlimited to, those disclosed herein. In some embodiments, other changesin cell biology (e.g., apoptosis) are detected.

Specifically, the present invention provides screening methods foridentifying modulators, i.e., candidate or test compounds or agents(e.g., proteins, peptides, peptidomimetics, peptoids, small molecules orother drugs) which bind to, or alter the signaling or functionassociated with the cancer markers of the present invention, have aninhibitory (or stimulatory) effect on, for example, stem cell cancermarker expression or cancer markers activity, or have a stimulatory orinhibitory effect on, for example, the expression or activity of acancer marker substrate. Compounds thus identified can be used tomodulate the activity of target gene products (e.g., stem cell cancermarker genes) either directly or indirectly in a therapeutic protocol,to elaborate the biological function of the target gene product, or toidentify compounds that disrupt normal target gene interactions.Compounds which inhibit the activity or expression of cancer markers areuseful in the treatment of proliferative disorders, e.g., cancer,particularly metastatic cancer or eliminating or controlling tumor stemcells to prevent or reduce the risk of cancer.

In one embodiment, the invention provides assays for screening candidateor test compounds that are substrates of a cancer markers protein orpolypeptide or a biologically active portion thereof. In anotherembodiment, the invention provides assays for screening candidate ortest compounds that bind to or modulate the activity of a cancer markerprotein or polypeptide or a biologically active portion thereof.

The test compounds of the present invention can be obtained using any ofthe numerous approaches in combinatorial library methods known in theart, including biological libraries; peptoid libraries (libraries ofmolecules having the functionalities of peptides, but with a novel,non-peptide backbone, which are resistant to enzymatic degradation butwhich nevertheless remain bioactive; see, e.g., Zuckennann et al., J.Med. Chem. 37: 2678-85 [1994]); spatially addressable parallel solidphase or solution phase libraries; synthetic library methods requiringdeconvolution; the ‘one-bead one-compound’ library method; and syntheticlibrary methods using affinity chromatography selection. The biologicallibrary and peptoid library approaches are preferred for use withpeptide libraries, while the other four approaches are applicable topeptide, non-peptide oligomer or small molecule libraries of compounds(Lam (1997) Anticancer Drug Des. 12:145).

Examples of methods for the synthesis of molecular libraries can befound in the art, for example in: DeWitt et al., Proc. Natl. Acad. Sci.U.S.A. 90:6909 [1993]; Erb et al., Proc. Nad. Acad. Sci. USA 91:11422[1994]; Zuckermann et al., J. Med. Chem. 37:2678 [1994]; Cho et al.,Science 261:1303 [1993]; Carrell et al., Angew. Chem. Int. Ed. Engl.33.2059 [1994]; Carell et al., Angew. Chem. Int. Ed. Engl. 33:2061[1994]; and Gallop et al., J. Med. Chem. 37:1233 [1994].

Libraries of compounds can be presented in solution (e.g., Houghten,Biotechniques 13:412-421 [1992]), or on beads (Lam, Nature 354:82-84[1991]), chips (Fodor, Nature 364:555-556 [1993]), bacteria or spores(U.S. Pat. No. 5,223,409; herein incorporated by reference), plasmids(Cull et al., Proc. Nad. Acad. Sci. USA 89:18651869 [1992]) or on phage(Scott and Smith, Science 249:386-390 [1990]; Devlin Science 249:404-406[1990]; Cwirla et al., Proc. Natl. Acad. Sci. 87:6378-6382 [1990];Felici, J. Mol. Biol. 222:301 [1991]).

In one embodiment, an assay is a cell-based assay in which a cell thatexpresses a stem cell cancer marker protein or biologically activeportion thereof is contacted with a test compound, and the ability ofthe test compound to the modulate cancer marker's activity isdetermined. Determining the ability of the test compound to modulatestem cell cancer marker activity can be accomplished by monitoring, forexample, changes in enzymatic activity. The cell, for example, can be ofmammalian origin.

The ability of the test compound to modulate cancer marker binding to acompound, e.g., a stem cell cancer marker substrate, can also beevaluated. This can be accomplished, for example, by coupling thecompound, e.g., the substrate, with a radioisotope or enzymatic labelsuch that binding of the compound, e.g., the substrate, to a cancermarker can be determined by detecting the labeled compound, e.g.,substrate, in a complex.

Alternatively, the stem cell cancer marker is coupled with aradioisotope or enzymatic label to monitor the ability of a testcompound to modulate cancer marker binding to a cancer markers substratein a complex. For example, compounds (e.g., substrates) can be labeledwith ¹²⁵I, ³⁵S ¹⁴C or ³H, either directly or indirectly, and theradioisotope detected by direct counting of radioemmission or byscintillation counting. Alternatively, compounds can be enzymaticallylabeled with, for example, horseradish peroxidase, alkaline phosphatase,or luciferase, and the enzymatic label detected by determination ofconversion of an appropriate substrate to product.

The ability of a compound (e.g., a stem cell cancer marker substrate) tointeract with a stem cell cancer marker with or without the labeling ofany of the interactants can be evaluated. For example, amicrophysiometer can be used to detect the interaction of a compoundwith a cancer marker without the labeling of either the compound or thecancer marker (McConnell et al. Science 257:1906-1912 [1992]). As usedherein, a “microphysiometer” (e.g., Cytosensor) is an analyticalinstrument that measures the rate at which a cell acidifies itsenvironment using a light-addressable potentiometric sensor (LAPS).Changes in this acidification rate can be used as an indicator of theinteraction between a compound and cancer markers.

In yet another embodiment, a cell-free assay is provided in which acancer marker protein or biologically active portion thereof iscontacted with a test compound and the ability of the test compound tobind to the stem cell cancer marker protein or biologically activeportion thereof is evaluated. Biologically active portions of the cancermarkers proteins to be used in assays of the present invention includefragments that participate in interactions with substrates or otherproteins, e.g., fragments with high surface probability scores.

Cell-free assays involve preparing a reaction mixture of the target geneprotein and the test compound under conditions and for a time sufficientto allow the two components to interact and bind, thus forming a complexthat can be removed and/or detected.

The interaction between two molecules can also be detected, e.g., usingfluorescence energy transfer (FRET) (see, for example, Lakowicz et al.,U.S. Pat. No. 5,631,169; Stavrianopoulos et al., U.S. Pat. No.4,968,103; each of which is herein incorporated by reference). Afluorophore label is selected such that a first donor molecule's emittedfluorescent energy will be absorbed by a fluorescent label on a second,‘acceptor’ molecule, which in turn is able to fluoresce due to theabsorbed energy.

Alternately, the ‘donor’ protein molecule can simply utilize the naturalfluorescent energy of tryptophan residues. Labels are chosen that emitdifferent wavelengths of light, such that the ‘acceptor’ molecule labelcan be differentiated from that of the ‘donor’. Since the efficiency ofenergy transfer between the labels is related to the distance separatingthe molecules, the spatial relationship between the molecules can beassessed. In a situation in which binding occurs between the molecules,the fluorescent emission of the ‘acceptor’ molecule label in 1 5 theassay should be maximal. An FRET binding event can be convenientlymeasured through standard fluorometric detection means well known in theart (e.g., using a fluorimeter).

In another embodiment, determining the ability of the stem cell cancermarkers protein to bind to a target molecule can be accomplished usingreal-time Biomolecular Interaction Analysis (BIA) (see, e.g., Sjolanderand Urbaniczky, Anal. Chem. 63:2338-2345 [1991] and Szabo et al. Curr.Opin. Struct. Biol. 5:699-705 [1995]). “Surface plasmon resonance” or“BIA” detects biospecific interactions in real time, without labelingany of the interactants (e.g., BIAcore). Changes in the mass at thebinding surface (indicative of a binding event) result in alterations ofthe refractive index of light near the surface (the optical phenomenonof surface plasmon resonance (SPR)), resulting in a detectable signalthat can be used as an indication of real-time reactions betweenbiological molecules.

In one embodiment, the target gene product or the test substance isanchored onto a solid phase. The target gene product/test compoundcomplexes anchored on the solid phase can be detected at the end of thereaction. The target gene product can be anchored onto a solid surface,and the test compound, (which is not anchored), can be labeled, eitherdirectly or indirectly, with detectable labels discussed herein.

It may be desirable to immobilize stem cell cancer markers, ananti-cancer marker antibody or its target molecule to facilitateseparation of complexed from non-complexed forms of one or both of theproteins, as well as to accommodate automation of the assay. Binding ofa test compound to a stem cell cancer marker protein, or interaction ofa cancer marker protein with a target molecule in the presence andabsence of a candidate compound, can be accomplished in any vesselsuitable for containing the reactants. Examples of such vessels includemicrotiter plates, test tubes, and micro-centrifuge tubes. In oneembodiment, a fusion protein can be provided which adds a domain thatallows one or both of the proteins to be bound to a matrix. For example,glutathione-S-transferase-cancer marker fusion proteins orglutathione-S-transferase/target fusion proteins can be adsorbed ontoglutathione Sepharose beads (Sigma Chemical, St. Louis, Mo.) orglutathione-derivatized microtiter plates, which are then combined withthe test compound or the test compound and either the non-adsorbedtarget protein or cancer marker protein, and the mixture incubated underconditions conducive for complex formation (e.g., at physiologicalconditions for salt and pH). Following incubation, the beads ormicrotiter plate wells are washed to remove any unbound components, thematrix immobilized in the case of beads, complex determined eitherdirectly or indirectly, for example, as described above.

Alternatively, the complexes can be dissociated from the matrix, and thelevel of cancer markers binding or activity determined using standardtechniques. Other techniques for immobilizing either cancer markersprotein or a target molecule on matrices include using conjugation ofbiotin and streptavidin. Biotinylated cancer marker protein or targetmolecules can be prepared from biotin-NHS (N-hydroxy-succinimide) usingtechniques known in the art (e.g., biotinylation kit, Pierce Chemicals,Rockford, Ill.), and immobilized in the wells of streptavidin-coated 96well plates (Pierce Chemical).

In order to conduct the assay, the non-immobilized component is added tothe coated surface containing the anchored component. After the reactionis complete, unreacted components are removed (e.g., by washing) underconditions such that any complexes formed will remain immobilized on thesolid surface. The detection of complexes anchored on the solid surfacecan be accomplished in a number of ways. Where the previouslynon-immobilized component is pre-labeled, the detection of labelimmobilized on the surface indicates that complexes were formed. Wherethe previously non-immobilized component is not pre-labeled, an indirectlabel can be used to detect complexes anchored on the surface; e.g.,using a labeled antibody specific for the immobilized component (theantibody, in turn, can be directly labeled or indirectly labeled with,e.g., a labeled anti-IgG antibody).

This assay is performed utilizing antibodies reactive with stem cellcancer marker protein or target molecules but which do not interferewith binding of the stem cell cancer markers protein to its targetmolecule. Such antibodies can be derivatized to the wells of the plate,and unbound target or cancer markers protein trapped in the wells byantibody conjugation. Methods for detecting such complexes, in additionto those described above for the GST-immobilized complexes, includeimmunodetection of complexes using antibodies reactive with the cancermarker protein or target molecule, as well as enzyme-linked assays whichrely on detecting an enzymatic activity associated with the cancermarker protein or target molecule.

Alternatively, cell free assays can be conducted in a liquid phase. Insuch an assay, the reaction products are separated from unreactedcomponents, by any of a number of standard techniques, including, butnot limited to: differential centrifugation (see, for example, Rivas andMinton, Trends Biochem Sci 18:284-7 [1993]); chromatography (gelfiltration chromatography, ion-exchange chromatography); electrophoresis(see, e.g., Ausubel et al., eds. Current Protocols in Molecular Biology1999, J. Wiley: New York.); and immunoprecipitation (see, for example,Ausubel et al., eds. Current Protocols in Molecular Biology 1999, J.Wiley: New York). Such resins and chromatographic techniques are knownto one skilled in the art (See e.g., Heegaard J. Mol. Recognit. 11:141-8[1998]; Hageand Tweed J. Chromatogr. Biomed. Sci. Appl 699:499-525[1997]). Further, fluorescence energy transfer can also be convenientlyutilized, as described herein, to detect binding without furtherpurification of the complex from solution.

The assay can include contacting the stem cell cancer markers protein orbiologically active portion thereof with a known compound that binds thecancer marker to form an assay mixture, contacting the assay mixturewith a test compound, and determining the ability of the test compoundto interact with a cancer marker protein, wherein determining theability of the test compound to interact with a cancer marker proteinincludes determining the ability of the test compound to preferentiallybind to cancer markers or biologically active portion thereof, or tomodulate the activity of a target molecule, as compared to the knowncompound.

To the extent that stem cell cancer markers can, in vivo, interact withone or more cellular or extracellular macromolecules, such as proteins,inhibitors of such an interaction are useful. A homogeneous assay can beused can be used to identify inhibitors.

For example, a preformed complex of the target gene product and theinteractive cellular or extracellular binding partner product isprepared such that either the target gene products or their bindingpartners are labeled, but the signal generated by the label is quencheddue to complex formation (see, e.g., U.S. Pat. No. 4,109,496, hereinincorporated by reference, that utilizes this approach forimmunoassays). The addition of a test substance that competes with anddisplaces one of the species from the preformed complex will result inthe generation of a signal above background. In this way, testsubstances that disrupt target gene product-binding partner interactioncan be identified. Alternatively, cancer markers protein can be used asa “bait protein” in a two-hybrid assay or three-hybrid assay (see, e.g.,U.S. Pat. No. 5,283,317; Zervos et al., Cell 72:223-232 [1993]; Maduraet al., J. Biol. Chem. 268.12046-12054 [1993]; Bartel et al.,Biotechniques 14:920-924 [1993]; Iwabuchi et al., Oncogene 8:1693-1696[1993]; and Brent WO 94/10300; each of which is herein incorporated byreference), to identify other proteins, that bind to or interact withcancer markers (“cancer marker-binding proteins” or “cancer marker-bp”)and are involved in cancer marker activity. Such cancer marker-bps canbe activators or inhibitors of signals by the cancer marker proteins ortargets as, for example, downstream elements of a cancermarkers-mediated signaling pathway.

Modulators of cancer markers expression can also be identified. Forexample, a cell or cell free mixture is contacted with a candidatecompound and the expression of cancer marker mRNA or protein evaluatedrelative to the level of expression of stem cell cancer marker mRNA orprotein in the absence of the candidate compound. When expression ofcancer marker mRNA or protein is greater in the presence of thecandidate compound than in its absence, the candidate compound isidentified as a stimulator of cancer marker mRNA or protein expression.Alternatively, when expression of cancer marker mRNA or protein is less(i.e., statistically significantly less) in the presence of thecandidate compound than in its absence, the candidate compound isidentified as an inhibitor of cancer marker mRNA or protein expression.The level of cancer markers mRNA or protein expression can be determinedby methods described herein for detecting cancer markers mRNA orprotein.

A modulating agent can be identified using a cell-based or a cell freeassay, and the ability of the agent to modulate the activity of a cancermarkers protein can be confirmed in vivo, e.g., in an animal such as ananimal model for a disease (e.g., an animal with prostate cancer ormetastatic prostate cancer; or an animal harboring a xenograft of aprostate cancer from an animal (e.g., human) or cells from a cancerresulting from metastasis of a prostate cancer (e.g., to a lymph node,bone, or liver), or cells from a prostate cancer cell line.

This invention further pertains to novel agents identified by theabove-described screening assays (See e.g., below description of cancertherapies). Accordingly, it is within the scope of this invention tofurther use an agent identified as described herein (e.g., a cancermarker modulating agent, an antisense cancer marker nucleic acidmolecule, a siRNA molecule, a cancer marker specific antibody, or acancer marker-binding partner) in an appropriate animal model (such asthose described herein) to determine the efficacy, toxicity, sideeffects, or mechanism of action, of treatment with such an agent.Furthermore, novel agents identified by the above-described screeningassays can be, e.g., used for treatments as described herein (e.g. totreat a human patient who has cancer).

Cancer Therapies

In some embodiments, the present invention provides therapies for cancer(e.g., breast cancer). In some embodiments, therapies target cancermarkers (e.g., including but not limited to, those shown in Tables 4-9).

Antibody Therapy

In some embodiments, the present invention provides antibodies thattarget tumors that express a stem cell cancer marker of the presentinvention (e.g., those shown in Tables 4-9). Any suitable antibody(e.g., monoclonal, polyclonal, or synthetic) can be utilized in thetherapeutic methods disclosed herein. In some embodiments, theantibodies used for cancer therapy are humanized antibodies. Methods forhumanizing antibodies are well known in the art (See e.g., U.S. Pat.Nos. 6,180,370, 5,585,089, 6,054,297, and 5,565,332; each of which isherein incorporated by reference).

In some embodiments, the therapeutic antibodies comprise an antibodygenerated against a stem cell cancer marker of the present invention,wherein the antibody is conjugated to a cytotoxic agent. In suchembodiments, a tumor specific therapeutic agent is generated that doesnot target normal cells, thus reducing many of the detrimental sideeffects of traditional chemotherapy. For certain applications, it isenvisioned that the therapeutic agents will be pharmacologic agents thatwill serve as useful agents for attachment to antibodies, particularlycytotoxic or otherwise anticellular agents having the ability to kill orsuppress the growth or cell division of endothelial cells. The presentinvention contemplates the use of any pharmacologic agent that can beconjugated to an antibody, and delivered in active form. Exemplaryanticellular agents include chemotherapeutic agents, radioisotopes, andcytotoxins. The therapeutic antibodies of the present invention caninclude a variety of cytotoxic moieties, including but not limited to,radioactive isotopes (e.g., iodine-131, iodine-123, technicium-99m,indium-111, rhenium-188, rhenium-186, gallium-67, copper-67, yttrium-90,iodine-125 or astatine-211), hormones such as a steroid, antimetabolitessuch as cytosines (e.g., arabinoside, fluorouracil, methotrexate oraminopterin; an anthracycline; mitomycin C), vinca alkaloids (e.g.,demecolcine; etoposide; mithramycin), and antitumor alkylating agentsuch as chlorambucil or melphalan. Other embodiments can include agentssuch as a coagulant, a cytokine, growth factor, bacterial endotoxin orthe lipid A moiety of bacterial endotoxin. For example, in someembodiments, therapeutic agents will include plant-, fungus- orbacteria-derived toxin, such as an A chain toxins, a ribosomeinactivating protein, α-sarcin, aspergillin, restrictocin, aribonuclease, diphtheria toxin or pseudomonas exotoxin, to mention justa few examples. In some embodiments, deglycosylated ricin A chain isutilized.

In any event, it is proposed that agents such as these can, if desired,be successfully conjugated to an antibody, in a manner that will allowtheir targeting, internalization, release or presentation to bloodcomponents at the site of the targeted tumor cells as required usingknown conjugation technology (See, e.g., Ghose et al., Methods Enzymol.,93:280 [1983]).

For example, in some embodiments the present invention providesimmunotoxins targeted a stem cell cancer marker of the presentinvention. Immunotoxins are conjugates of a specific targeting agenttypically a tumor-directed antibody or fragment, with a cytotoxic agent,such as a toxin moiety. The targeting agent directs the toxin to, andthereby selectively kills, cells carrying the targeted antigen. In someembodiments, therapeutic antibodies employ crosslinkers that providehigh in vivo stability (Thorpe et al., Cancer Res., 48:6396 [1988]).

In other embodiments, particularly those involving treatment of solidtumors, antibodies are designed to have a cytotoxic or otherwiseanticellular effect against the tumor vasculature, by suppressing thegrowth or cell division of the vascular endothelial cells. This attackis intended to lead to a tumor-localized vascular collapse, deprivingthe tumor cells, particularly those tumor cells distal of thevasculature, of oxygen and nutrients, ultimately leading to cell deathand tumor necrosis.

In some embodiments, antibody based therapeutics are formulated aspharmaceutical compositions as described below. In some embodiments,administration of an antibody composition of the present inventionresults in a measurable decrease in cancer (e.g., decrease orelimination of tumor).

Pharmaceutical Compositions

The present invention further provides pharmaceutical compositions(e.g., comprising a small molecule, antisense, antibody, or siRNA thattargets the stem cell cancer markers of the present invention). Thepharmaceutical compositions of the present invention can be administeredin a number of ways depending upon whether local or systemic treatmentis desired and upon the area to be treated. Administration can betopical (including ophthalmic and to mucous membranes including vaginaland rectal delivery), pulmonary (e.g., by inhalation or insufflation ofpowders or aerosols, including by nebulizer; intratracheal, intranasal,epidermal and transdermal), oral or parenteral. Parenteraladministration includes intravenous, intraarterial, subcutaneous,intraperitoneal or intramuscular injection or infusion; or intracranial,e.g., intrathecal or intraventricular, administration.

Pharmaceutical compositions and formulations for topical administrationcan include transdermal patches, ointments, lotions, creams, gels,drops, suppositories, sprays, liquids and powders. Conventionalpharmaceutical carriers, aqueous, powder or oily bases, thickeners andthe like can be necessary or desirable.

Compositions and formulations for oral administration include powders orgranules, suspensions or solutions in water or non-aqueous media,capsules, sachets or tablets. Thickeners, flavoring agents, diluents,emulsifiers, dispersing aids or binders can be desirable.

Compositions and formulations for parenteral, intrathecal orintraventricular administration can include sterile aqueous solutionsthat can also contain buffers, diluents and other suitable additivessuch as, but not limited to, penetration enhancers, carrier compoundsand other pharmaceutically acceptable carriers or excipients.

Pharmaceutical compositions of the present invention include, but arenot limited to, solutions, emulsions, and liposome-containingformulations. These compositions can be generated from a variety ofcomponents that include, but are not limited to, preformed liquids,self-emulsifying solids and self-emulsifying semisolids.

The pharmaceutical formulations of the present invention, which canconveniently be presented in unit dosage form, can be prepared accordingto conventional techniques well known in the pharmaceutical industry.Such techniques include the step of bringing into association the activeingredients with the pharmaceutical carrier(s) or excipient(s). Ingeneral the formulations are prepared by uniformly and intimatelybringing into association the active ingredients with liquid carriers orfinely divided solid carriers or both, and then, if necessary, shapingthe product.

The compositions of the present invention can be formulated into any ofmany possible dosage forms such as, but not limited to, tablets,capsules, liquid syrups, soft gels, suppositories, and enemas. Thecompositions of the present invention can also be formulated assuspensions in aqueous, non-aqueous or mixed media. Aqueous suspensionscan further contain substances that increase the viscosity of thesuspension including, for example, sodium carboxymethylcellulose,sorbitol and/or dextran. The suspension can also contain stabilizers.

In one embodiment of the present invention the pharmaceuticalcompositions can be formulated and used as foams. Pharmaceutical foamsinclude formulations such as, but not limited to, emulsions,microemulsions, creams, jellies and liposomes. While basically similarin nature these formulations vary in the components and the consistencyof the final product.

Agents that enhance uptake of oligonucleotides at the cellular level canalso be added to the pharmaceutical and other compositions of thepresent invention. For example, cationic lipids, such as lipofectin(U.S. Pat. No. 5,705,188), cationic glycerol derivatives, andpolycationic molecules, such as polylysine (WO 97/30731), also enhancethe cellular uptake of oligonucleotides.

The compositions of the present invention can additionally contain otheradjunct components conventionally found in pharmaceutical compositions.Thus, for example, the compositions can contain additional, compatible,pharmaceutically-active materials such as, for example, antipruritics,astringents, local anesthetics or anti-inflammatory agents, or cancontain additional materials useful in physically formulating variousdosage forms of the compositions of the present invention, such as dyes,flavoring agents, preservatives, antioxidants, opacifiers, thickeningagents and stabilizers. However, such materials, when added, should notunduly interfere with the biological activities of the components of thecompositions of the present invention. The formulations can besterilized and, if desired, mixed with auxiliary agents, e.g.,lubricants, preservatives, stabilizers, wetting agents, emulsifiers,salts for influencing osmotic pressure, buffers, colorings, flavoringsand/or aromatic substances and the like which do not deleteriouslyinteract with the nucleic acid(s) of the formulation.

Certain embodiments of the invention provide pharmaceutical compositionscontaining (a) one or more compounds that modulate the activity of astem cell caner marker (e.g. antibody, small molecule, siRNA,anti-sense, etc.) and (b) one or more other chemotherapeutic agents.Examples of such chemotherapeutic agents include, but are not limitedto, anticancer drugs such as daunorubicin, dactinomycin, doxorubicin,bleomycin, mitomycin, nitrogen mustard, chlorambucil, melphalan,cyclophosphamide, 6-mercaptopurine, 6-thioguanine, cytarabine (CA),5-fluorouracil (5-FU), floxuridine (5-FUdR), methotrexate (MTX),colchicine, vincristine, vinblastine, etoposide, teniposide, cisplatinand diethylstilbestrol (DES). Anti-inflammatory drugs, including but notlimited to nonsteroidal anti-inflammatory drugs and corticosteroids, andantiviral drugs, including but not limited to ribivirin, vidarabine,acyclovir and ganciclovir, can also be combined in compositions of theinvention. Other chemotherapeutic agents are also within the scope ofthis invention. Two or more combined compounds can be used together orsequentially.

Dosing is dependent on severity and responsiveness of the disease stateto be treated, with the course of treatment lasting from several days toseveral months, or until a cure is effected or a diminution of thedisease state is achieved (e.g. reduction in tumor size). Optimal dosingschedules can be calculated from measurements of drug accumulation inthe body of the patient. The administering physician can easilydetermine optimum dosages, dosing methodologies and repetition rates.Optimum dosages can vary depending on the relative potency of individualoligonucleotides, and can generally be estimated based on EC₅₀s found tobe effective in in vitro and in vivo animal models or based on theexamples described herein. In general, dosage is from 0.01 μg to 100 gper kg of body weight, and can be given once or more daily, weekly,monthly or yearly. The treating physician can estimate repetition ratesfor dosing based on measured residence times and concentrations of thedrug in bodily fluids or tissues. Following successful treatment, it canbe desirable to have the subject undergo maintenance therapy to preventthe recurrence of the disease state, wherein the oligonucleotide isadministered in maintenance doses, ranging from 0.01 μg to 100 g per kgof body weight, once or more daily, to once every 20 years.

Transgenic Animals Expressing Cancer Marker Genes

The present invention contemplates the generation of transgenic animalscomprising an exogenous cancer marker gene of the present invention ormutants and variants thereof (e.g., truncations or single nucleotidepolymorphisms) or knock-outs thereof. In some embodiments, thetransgenic animal displays an altered phenotype (e.g., increased ordecreased presence of markers) as compared to wild-type animals. Methodsfor analyzing the presence or absence of such phenotypes include but arenot limited to, those disclosed herein. In some embodiments, thetransgenic animals further display an increased or decreased growth oftumors or evidence of cancer.

The transgenic animals of the present invention find use in drug (e.g.,cancer therapy) screens. In some embodiments, test compounds (e.g., adrug that is suspected of being useful to treat cancer) and controlcompounds (e.g., a placebo) are administered to the transgenic animalsand the control animals and the effects evaluated.

The transgenic animals can be generated via a variety of methods. Insome embodiments, embryonal cells at various developmental stages areused to introduce transgenes for the production of transgenic animals.Different methods are used depending on the stage of development of theembryonal cell. The zygote is the best target for micro-injection. Inthe mouse, the male pronucleus reaches the size of approximately 20micrometers in diameter that allows reproducible injection of 1-2picoliters (pl) of DNA solution. The use of zygotes as a target for genetransfer has a major advantage in that in most cases the injected DNAwill be incorporated into the host genome before the first cleavage(Brinster et al., 1985, PNAS 82:4438-4442). As a consequence, all cellsof the transgenic non-human animal will carry the incorporatedtransgene. This will in general also be reflected in the efficienttransmission of the transgene to offspring of the founder since 50% ofthe germ cells will harbor the transgene. U.S. Pat. No. 4,873,191describes a method for the micro-injection of zygotes; the disclosure ofthis patent is incorporated herein in its entirety.

In other embodiments, retroviral infection is used to introducetransgenes into a non-human animal. In some embodiments, the retroviralvector is utilized to transfect oocytes by injecting the retroviralvector into the perivitelline space of the oocyte (U.S. Pat. No.6,080,912, incorporated herein by reference). In other embodiments, thedeveloping non-human embryo can be cultured in vitro to the blastocyststage. During this time, the blastomeres can be targets for retroviralinfection (Janenich, 1976, PNAS 73:1260). Efficient infection of theblastomeres is obtained by enzymatic treatment to remove the zonapellucida (Hogan et al., in Manipulating the Mouse Embryo, Cold SpringHarbor Laboratory Press, Cold Spring Harbor, N.Y. [1986]). The viralvector system used to introduce the transgene is typically areplication-defective retrovirus carrying the transgene (Jahner et al.,1985, PNAS 82:6927). Transfection is easily and efficiently obtained byculturing the blastomeres on a monolayer of virus-producing cells(Stewart, et al., 1987, EMBO J., 6:383).

Alternatively, infection can be performed at a later stage. Virus orvirus-producing cells can be injected into the blastocoele (Jahner etal., 1982, Nature 298:623). Most of the founders will be mosaic for thetransgene since incorporation occurs only in a subset of cells that formthe transgenic animal. Further, the founder can contain variousretroviral insertions of the transgene at different positions in thegenome that generally will segregate in the offspring. In addition, itis also possible to introduce transgenes into the germline, albeit withlow efficiency, by intrauterine retroviral infection of the midgestationembryo (Jahner et al., supra [1982]). Additional means of usingretroviruses or retroviral vectors to create transgenic animals known tothe art involve the micro-injection of retroviral particles or mitomycinC-treated cells producing retrovirus into the perivitelline space offertilized eggs or early embryos (PCT International Application WO90/08832 [1990], and Haskell and Bowen, 1995, Mol. Reprod. Dev.,40:386).

In other embodiments, the transgene is introduced into embryonic stemcells and the transfected stem cells are utilized to form an embryo. EScells are obtained by culturing pre-implantation embryos in vitro underappropriate conditions (Evans et al., 1981, Nature 292:154; Bradley etal., 1984, Nature 309:255; Gossler et al., 1986, PNAS 83:9065; andRobertson et al., 1986, Nature 322:445). Transgenes can be efficientlyintroduced into the ES cells by DNA transfection by a variety of methodsknown to the art including calcium phosphate co-precipitation,protoplast or spheroplast fusion, lipofection and DEAE-dextran-mediatedtransfection. Transgenes can also be introduced into ES cells byretrovirus-mediated transduction or by micro-injection. Such transfectedES cells can thereafter colonize an embryo following their introductioninto the blastocoel of a blastocyst-stage embryo and contribute to thegerm line of the resulting chimeric animal (for review, See, Jaenisch,Science, 1988, 240:1468). Prior to the introduction of transfected EScells into the blastocoel, the transfected ES cells can be subjected tovarious selection protocols to enrich for ES cells which have integratedthe transgene assuming that the transgene provides a means for suchselection. Alternatively, the polymerase chain reaction can be used toscreen for ES cells that have integrated the transgene. This techniqueobviates the need for growth of the transfected ES cells underappropriate selective conditions prior to transfer into the blastocoel.

In still other embodiments, homologous recombination is utilized toknock-out gene function or create deletion mutants (e.g., truncationmutants). Methods for homologous recombination are described in U.S.Pat. No. 5,614,396, incorporated herein by reference.

EXPERIMENTAL

The following examples are provided in order to demonstrate and furtherillustrate certain embodiments and aspects of the present invention andare not to be construed as limiting the scope thereof.

In the experimental disclosure which follows, the followingabbreviations apply: N (normal); M (molar); mM (millimolar); μM(micromolar); mol (moles); mmol (millimoles); μmol (micromoles); nmol(nanomoles); pmol (picomoles); g (grams); mg (milligrams); μg(micrograms); ng (nanograms); l or L (liters); ml (milliliters); μl(microliters); cm (centimeters); mm (millimeters); μm (micrometers); nm(nanometers); ° C. (degrees Centigrade); i.p. (intraperitoneal); HBSS(Hepes buffered saline solution); FCS (fetal calf serum); FBS (fetalbovine serum).

Example 1 Isolation of Colon Cancer Stem Cells

Recently it has been demonstrated that malignant human breast tumorsharbor a small, distinct population of cancer stem cells that areenriched for the ability to form tumors in immunodeficient mice. AnESA+, CD44+, CD24−/low, Lin− cell population was found to be 50-foldenriched for tumorigenic breast tumor cells compared to unfractionatedtumor cells (Al-Hajj et al., 2003, PNAS 100:3983-8). This exampledescribes the identification of a cancer stem cell population incolorectal cancers.

To identify colon cancer stem cells, a tumor sample from a patientbiopsy of a colorectal carcinoma minimally passaged in immunocompromisedmice was examined. Tumor cells were removed under sterile conditions,cut into small pieces, and minced completely using sterile blades.Single cell suspensions were then obtained by enzymatic digestion andmechanical disruption. Specifically, minced tumor pieces were mixed withCollagenase/Hyaluronidase, supplemented with Dispase, in culture mediumand incubated at 37° C. for 2 hours with pipetting up and down through a10-mL pipette every 15-20 min. Digested cells were filtered through a 40uM nylon mesh, washed with RPMI/10% FBS, and washed twice with HBSS/2%FBS and 25 mM HEPES.

Single cell tumor suspensions were next sorted into tumorigenic andnon-tumorigenic cells based on cell surface markers. Cells were counted,washed twice with HBSS containing 2% heat-inactivated calf serum (HICS)and 25 mM HEPES, and resuspended at 10⁶ cells per 100 ul. Tumor cellswere incubated with rat anti-mouse H2K^(d), CD3, CD4, CD8, Ter119, Mac1and Gr1 antibodies conjugated to magnetic beads and, applied to a strongmagnet to remove mouse hematopoietic and stromal cells. In certainembodiments, bulk tumor cells can be depleted of murine cells usingbiotin-conjugated anti-H2 K^(d) and murine CD45, followed by conjugationto strepavidin-conjugated magnetic beads and application to a strongmagnet. Tumors cells were then incubated with either sheep anti-rat orStrepatividin antibodies conjugated to Cy5.5-PE and the viability dyepropidium iodide (PI) to detect and enable exclusion of remaining mousehematopoietic/stromal cells and dead cells, respectively. Cells werefurther incubated with fluorescently conjugated antibodies against humanESA (Miltenyi Biotec; Auburn, Calif.) and CD44, (Bioscience, San Diego,Calif.) to positively select human tumor cells expressing ESA and CD44.Flow cytometry was performed on a FACSAria (Becton Dickinson, FranklinLakes, N.J.) with the use of side and forward scatter profiles toexclude doublets and cell clumps. Cy5.5-PE+ and PI positive cells werefirst excluded and a fraction of ESA+ 44+ cells was isolatedindependently of a fraction of non-ESA+44+ tumor cells (FIG. 1).

The tumorigenicity of isolated ESA+44+ colon tumor cells compared tonon-ESA+, CD44+ colon tumor cells was next determined. Isolated ESA+44+tumor cells versus non-ESA+44+ tumor cells at approximately 1,000 cellsper animal were injected subcutaneously into NOD/SCID mice. Tumors wereallowed to grow and tumor volumes were assessed weekly. Only miceinjected with ESA+44+ cells developed tumors (FIG. 2), demonstrating adramatic enrichment for tumorigenic cancer stem cells. Tumors wereconsistently obtained upon injection of as few as 100 ESA+CD44+ cells(FIG. 2B & Table 2). TABLE 2 Tumors/Injections 2000 1000 500 250 200 10040 UM-C4 ESA⁺CD44⁺ 5/5  11/12 17/20 — 29/33 10/10 11/32 ESA⁺CD44⁻ 0/20 2/24 0/4 —  0/20 — — ESA⁺CD44⁺ALDH⁺ — — 5/5 5/7 — — — ESA⁺CD44⁺ALDH⁻ —— 0/5 0/6 — — — ESA⁺CD44⁻ALDH⁺ — — 0/5 0/6 — — — UM-C6 ESA⁺CD44⁺ 4/4 5/5 10/10 —  7/11 — — ESA⁺CD44⁻ 0/10  0/10 — — 0/4 — — ESA⁺CD44⁺ALDH⁺ ——  3/13 2/9 — — — ESA⁺CD44⁺ALDH⁻ — — 2/2 2/8 — — — ESA⁺CD44⁻ALDH⁺ — — 0/10 0/7 — — — OMP-C5 ESA⁺CD44⁺ 4/5  —  7/10 — — — — ESA⁺CD44⁻ 0/10 — —— — — — ESA⁺ALDH⁺ — — 3/9 — — — — ESA⁺ALDH⁻ — —  1/11 — — — — OMP-C8ESA⁺CD44⁺ 5/5  4/4  5/10 — — —  2/10 ESA⁺CD44⁻ 1/15 — — — — — —ESA⁺CD44⁺ALDH⁺ — —  5/11 — — — — ESA⁺CD44⁺ALDH⁻ — —  6/13 — — — —ESA⁺CD44⁻ALDH⁺ — — 0/2 — — — —

Following tumor growth out to over 80 days revealed continuing growth oftumors generated by ESA+44+ tumor cells, but only rarely (3/89) weretumors formed in mice injected with ESA+, CD44− or ESA−CD44− tumor cellsat doses of 1000 or more (FIG. 2 and Table 2). These rare tumors fromNTG cells, observed only at higher cell doses, likely result from cellsorting impurities (˜0.5%). Importantly, the tumors generated by theESA+CD44+ colon cancer stem cells were phenotypically similar to thetumors from which the colon cancer stem cells were isolated (FIG. 3).

Example 2 Identification of Colon Cancer Stem Cell Markers by MicroarrayAnalysis

Following the successful isolation of colon cancer stem cells,microarray analysis was utilized to identify markers for colon cancerstem cells versus non-tumorigenic tumor cells. Presorted tumor cells,tumorigenic cancer stem cells, and sorted non-tumorigenic solid tumorcells were isolated and separated by FACS as described above induplicate. Total RNA was isolated from the different cell populationsusing RNeasy (Qiagen, Valencia, Calif.) according to the manufacturer'sprotocol. Probes for microarray analysis were prepared and hybridized toAffymetrix HG-U133 gene chips according to Affymetrix protocols(Affymetrix, Santa Clara, Calif.). Arrays were scanned with an argon-ionlaser confocal microscope and the intensity for each probe set on thearray was assessed with Affymetrix Microarray Suite 4.0 softwareaccording to Affymetrix procedures.

Genes identified by microarray analysis as having increased expressionin colon cancer stem cells compared with non-tumorigenic tumor cells(FIG. 4A), both of which populations were isolated by FACS, are listedin Table 1. These genes serve as a gene expression profile of coloncancer stem cells and find use in markers of colon cancer stem cells.Included in this list is the Notch pathway target genes HES1 and HES6.HES6, in particular, was found to be expressed in isolated tumorigeniccolon stem cells at 6-fold higher levels than in FACS sortednon-tumorigenic tumor cells (FIG. 5A). This suggests that activation ofthe Notch pathway is important to the biological function of coloncancer stem cells and highlights Hes6 and/or HES1 as a unique marker ofNotch activation in this rare cell population.

To validate microarray data, RNA was independently isolated fromFACS-purified colon cancer stem cells and non-tumorigenic cells andrelative gene expression was assessed using Taqman assay quantitativeRT-PCR. Using purified cell populations from UM-C4 colon cancer cells,for example, HES1 was shown to be increased in TG versus NTG cells (FIG.5B). An additional subset of colon cancer stem cell genes was alsoassessed in this manner, demonstrating that whereas ATOH1, BMPR1A, CDH1,EPHB2, MYB, MYC, SOX9 and STRAP were verified to be increased in TGversus NTG cells, TCF₄ and VIM were consistently lower in colon cancerstem cells versus NTG cells (FIG. 4B).

Example 3 Analysis of HES6 Expression by Colon Cancer Stem Cells

The identification of HES6 expression as upregulated in tumorigenicESA+44+ colon tumor cells compared to non-tumorigenic colon tumor cellsenables the use of HES6 to enrich further for colon cancer stem cells.To examine HES6 expression by ESA+44+ tumorigenic colon stem cells, theHES6 promoter is used to control expression of the marker protein GFP incolon tumor cells and cells are sorted based on cell surface expressionof ESA and CD44 as well as GFP expression.

To generate a HES6 regulated GFP reporter construct, the endogenous HES6promoter is isolated from genomic human DNA and ligated 5′ to a GFPexpression cassette and then incorporated into the ViraPower™ LentiviralExpression System (Invitrogen, Carlsbad, Calif.) using standardrecombinant DNA techniques. Viral particles are generated according tothe manufacturer's protocol and used to infect colon tumor stem cellsisolated as described in detail above. Infected tumor stem cells arerepassaged into immunocompromised mice to grow tumors that can then beanalyzed for ESA, CD44, and GFP expression.

Tumors generated by HES6-GFP infected colon cancer stem cells areisolated and single cell suspensions generated as described above.Single cell tumor suspensions are then sorted into tumorigenic andnon-tumorigenic cells based on the cell surface markers ESA and CD44 asdescribed above and further sorted for GFP expression to determine thepercentage of ESA+44+ colon cancer stem cells that express HES6 asindicated by GFP+ cells.

If the ESA+44+ cancer stem cell populations contains both GFP− and GFP+cell populations, the tumorigenicity of these different cell populationswill be determined. Specifically, isolated ESA+44+GFP+ versusESA+44+GFP− cells are injected subcutaneously NOD/SCID mice atapproximately 1,000; 500; and 250 cells per animal. Differences in thenumber of injected cells required for consistent tumor formation in micewill determine if selecting for expression of GFP driven by the HES6promoter further enriches for tumorigenic tumor cells.

Example 4 HES6-GFP Based Assays to Analyze the Effects of TherapeuticCompounds on Colon Cancer Stem Cells

Successful use of the HES6 promoter to drive expression of GFP in coloncancer stem cells enables the use of HES6-GFP based assays to examinethe effects of potential therapeutic compounds on the properties ofcolon cancer stem cells. Colon cancer stem cells can be easily detectedbased on GFP expression and increases or decreases in the numbers ofGFP+ colon cancer stem cells determined following treatment with apotential therapeutic compound.

Colon cancer stem cells are isolated and infected with HES-GFPlentivirus as described in detail above and injected subcutaneously intoimmunodeficient mice. Animals are then either immediately treated withthe potential therapeutic compound such as, for example, an antibodyagainst a colon cancer stem cell marker, or palpable tumors are allowedto grow and treatment with the compound is then initiated. Thus, forexample, naked anti-PTGFRN antibodies or control antibodies are injectedi.p. twice a week for six weeks. Following antibody treatment, tumorsare harvested and dissociated into single cell suspension as describedabove, and FACS analysis performed to detect GFP+ colon cancer stemcells. The presence and number of colon cancer stem cells in tumors fromanimals treated with anti-PTGFRN antibodies versus control antibodies isthus determined.

Example 5 HES6-Luciferase Reporter Assays

The endogenous HES6 promoter contains three cbf transcriptional bindingdomains indicating that like HES1, with a promoter that contains asingle cbf binding domain, HES6 expression is directly regulated byactivation of the Notch signaling pathway. Identification of HES6 as acolon cancer stem cell marker enables the use of the HES6 promoter as areporter for Notch activation in, for example, luciferase based reporterassays to characterize the Notch pathway activation of HES6 and tomeasure the effect of compounds on activating or inhibiting the Notchsignaling pathway.

To generate Notch luciferase reporters, the endogenous HES6 promoter isisolated from genomic human DNA and ligated 5′ to a firefly luciferaseexpression cassette in an expression plasmid vector using standardrecombinant techniques. In addition the HES6 promoter luciferasepolynucleotide is incorporated into the ViraPower™ Lentiviral ExpressionSystem (Invitrogen, Carlsbad, Calif.) and viral particles generatedaccording to the manufacturer's protocol. As a control, mutantHES6-luciferase reporter vectors are generated that contain mutationswithin the three cbf transcription binding domains that disrupt RBP-Jbinding to the HES6 promoter.

In one embodiment of the invention, an in vitro luciferase assay is usedto characterize the Notch pathway activation of HES6 by determiningwhich of the four Notch receptors are involved in HES6 expression.HEK293 cells cultured in DMEM supplemented with antibiotics and 10% FCSare co-transfected with: 1) the wild-type or mutant HES6-luciferasereporter vector to measure levels of Notch signaling; 2) a Renillaluciferase reporter (Promega; Madison, Wis.) as an internal control fortransfection efficiency; and 3) an expression vector encoding one of thefour Notch receptors or a negative control. Forty-eight hours followingtransfection, luciferase levels are measured using a dual luciferaseassay kit (Promega; Madison, Wis.) with firefly luciferase activitynormalized to Renilla luciferase activity. Levels of enhanced Notchsignaling over endogenous levels by heterologous expression of each ofthe Notch receptors will help determine which of these receptors isinvolved in HES6 activation in colon cancer stem cells.

In another embodiment of the invention, an in vitro luciferase assay isused to determine the effect of different molecules on Notch signaling.HEK293 cells cultured in DMEM supplemented with antibiotics and 10% FCSare co-transfected with: 1) the wild-type or mutant HES6-luciferasereporter vector to measure levels of Notch signaling and 2) a Renillaluciferase reporter (Promega; Madison, Wis.) as an internal control fortransfection efficiency. Furthermore, an expression vector encoding aNotch receptor is transfected to boost endogenous Notch signaling in thecultured cells. Twenty-four hours following transfection, the moleculebeing tested for an effect on Notch signaling such as, for example, anantibody against a Notch receptor, or a negative control molecule areadded to the cell culture medium, and after eight hours, luciferaselevels are measured using a dual luciferase assay kit (Promega; Madison,Wis.). Three independent experiments are performed in triplicate. Theability of different compounds to activate or inhibit the Notchsignaling pathway in vitro is thus determined.

In yet another embodiment, compounds that inhibit the Notch signalingpathway the in vitro assay are used in an in vivo luciferase assay todetermine the effect on colon cancer stem cells. Colon cancer stem cellsisolated as described above are infected with wild-type or mutantHES6-luciferase lentiviruses, and the infected tumor cells injected intothe mammary fat pads of VP-16 and estrogen pre-treated immunodeficientmice. Animals are then either immediately treated with the Notchinhibitory molecule such as, for example, an antibody against a Notchreceptor, or palpable tumors are allowed to grow and then treatment ofthe inhibitory compound is initiated. Primary tumor growth and distalmetastases are then monitored over time for luciferase activity in livemice using bioluminescent imaging. The ability of different compoundthat inhibit Notch signaling to stop or slow cancer stem cellproliferation and metastasis in vivo is thus determined.

Example 6 Quantitative RT-PCR Assays Using HES6 to Detect the Number ofColon Cancer Stem Cells in a Tumor Sample

The identification of HES6 as a marker of colon cancer stem cellsenables its use in determining the number of cancer stem cells presentin a tumor sample by TaqMan analysis. Such an analysis could beundertaken to examine, for example, the effect of experimental compoundson cancer stem cell proliferation or survival. Also contemplated is theanalysis of a patient tumor sample in order to diagnosis a tumor and/orprovide a prognosis.

TaqMan oligonucleotide primers and probes that specifically hybridize toand amplify a region of HES6 mRNA over an exon-intron junction aredesigned using Primer Express Software (Applied Biosystems; Foster City,Calif.) and their specificity confirmed using conventional RT-PCRtechniques. Colon cancer stem cell are isolated as described above andtotal RNA extracted using RNasy (Qiagen, Valencia, Calif.) according tothe manufacturer's protocol. Using Applied Biosystems 7300 Real-Time PCRSystem and TaqMan One-Step RT-PCR Master Mix Reagents Kit a standardcurve of the average amount of HES6 mRNA expressed in a microgram of RNAfrom a known number of colon cancer stem cells is determined. Serial10-fold dilutions of RNA from isolated colon cancer stem cells with RNAfrom a cell population that does not express detectable levels of HES6are used to generate the standard curve. Expression levels arenormalized to the housekeeping gene GAPDH. Colon cancer samples with anunknown number of cancer stem cells can be compared to a simultaneouslygenerated standard curve to determine the number of cancer stem cells inthe sample.

In one embodiment of the present invention, TaqMan analysis can be usedto examine the effect of a compound on the proliferation and survival ofcolon cancer stem cells. Colon cancer stem cells isolated as describedabove are injected subcutaneously into NOD/SCID mice. Tumor cells areallowed to grow into palpable tumors at which point animals are treatedwith a potential therapeutic compound such as, for example, an antibodyagainst colon cancer stem cell marker disclosed in Table 1. Thus, forexample, naked anti-MET receptor antibodies or control antibodies areinjected i.p. twice a week for two to three weeks. Tumors are thenharvested from MET antibody and control injected mice and total RNAisolated from tumors using RNasy (Qiagen, Valencia, Calif.) according tothe manufacturer's protocol. The number of HES6 positive colon cancerstem cells from each tumor in the different experimental groups is thendetermined by TaqMan analysis compared to a standard curve of HES6expression in colon cancer stem cells generated as described above. Adecrease in the number of colon cancer stem cells in the anti-METantibody treated group suggests that the therapeutic compound has adirect effect on the survival and/or proliferation of colon cancer stemcells.

In another embodiment of the invention, TaqMan analysis can be used todetermine the number of colon cancer stem cells in a patient sample. RNAis extracted as described above from a fresh or historical tumor biopsyof a colon cancer, and the number of HES6 positive colon cancer stemcells in the sample determined by comparison with a standard curve ofHES6 expression in colon cancer stem cells generated as described above.Such an analysis finds use in diagnosing a colon cancer, providing aprognosis of a colon cancer, analyzing the effects of differenttherapeutics on a colon cancer, and prescribing a therapeutic thattargets colon cancer stem cells.

Example 7

Identification of CEACAM6 as a Marker of Colon Cancer Stem Cells

Genes identified by microarray analysis as having increased expressionin colon cancer stem cells compared with non-tumorigenic sorted tumorcells are shown in Table 1. These genes serve as a gene expressionprofile of colon cancer stem cells and find use as markers of coloncancer stem cells. Included in this list is the immunoglobulinsuperfamily member adhesion molecule CEACAM6 (FIG. 6). Analysis byFACSAria of colon tumor cells as described above showed a definite shiftin mean fluorescence intensity associated with addition of a monoclonalCEACAM6 antibody (Alexis Biochemicals; clone GM7G5; FIG. 7A).Furthermore, CEACAM6 was heterogeneously expressed in colon tumor cells(FIG. 7B).

Example 8 Purification of Colon Cancer Stem Cells based on Expression ofCEACAM6

The identification of increased expression of CEACAM6 in colon cancerstem cells suggests its use as a marker to further purify stem cellsfrom total tumor cell populations. To determine if CEACAM6 expressionidentifies a tumorigenic colon cancer stem cell population, colon cellsare sorted based on expression of ESA, CD44, and CEACAM6 and thetumorigenicity of different sorted cell populations is assessed inimmunodeficient mice.

Tumors are isolated and dissociated into single cell tumor suspensionsas described above. These cells are next sorted as described in detailabove into ESA+44+ colon cancer stem cells; ESA+44− non-tumorigeniccolon tumor cells; ESA+44+CEACAM6+; and ESA+44+CEACAM6− cellpopulations. The tumorigenicity of these different isolated colon tumorcells is then determined by injected limiting dilutions of tumor cellsinto NOD/SCID mice. Tumors are allowed to grow and, starting at aroundday 30, tumor volumes measured.

Example 9 Identification of CD166 as a Marker of Colon Cancer Stem Cells

Genes identified by microarray analysis as having increased expressionin colon cancer stem cells compared with non-tumorigenic sorted tumorcells are shown in Table 1. These genes serve as a gene expressionprofile of colon cancer stem cells and find use as markers of coloncancer stem cells. Included in this list is the immunoglobulinsuperfamily member adhesion molecule CD166. FACSAria of colon tumorcells as described above showed CD166 expression in 19.8% of colon tumorcells and greater than 92% of ESA+44+ colon cancer stem cells (FIG. 8).

Example 10 Purification of Colon Cancer Stem Cells based on Expressionof CD166

The identification of increased expression of CD166 in colon cancer stemcells suggests its use as a marker to further purify stem cells fromtotal tumor cell populations. To determine if CD166 expressionidentifies a tumorigenic colon cancer stem cell population, colon cellswere sorted based on expression of ESA, CD44, and CD166 and thetumorigenicity was assessed in immunodeficient mice.

Tumors were isolated and dissociated into single cell tumor suspensionsas described above. These cells were next sorted as described in detailabove into ESA+44+166+; ESA+ 44+ 166−; ESA+44−166+; and ESA+44−166− cellpopulations. Two hundred cells from each isolated colon tumor cellpopulation were injected into NOD/SCID mice.

Example 11 Colon Cancer Stem Cells Display Elevated Levels of ALDHActivity and Gene Expression

To determine whether colon tumor cells contain ALDH activity, primaryxenograft tumors depleted of murine cells (using antibodies against CD45and H2K^(d)) were screened using the Aldefluor™ reagent. The majority ofCD44⁺ cells, approximately 85%, contained ALDH activity levelsdetectably higher than the bulk of colon tumor cells (FIG. 9A).Consistent with this observation, microarray analyses indicated that TGUM-C4, UM-C6, and OMP-C9 TG cells express several ALDH family members(e.g. ALDH1A1, ALDH1B1, ALDH2, ALDH3A2, ALDH5A1, ALDH6 μl, ALDH7A1,ALDH9A1 & ALDH18A1) at higher levels than NTG populations (FIGS. 10A &B). Following isolation of ALDH and CD44 subpopulations from UM-C4tumors by dissociation and FACS, only the ESA⁺44⁺ALDH⁺ subpopulationcontained TG ability upon transplantation (FIG. 9B; Table 2). Incontrast to ESA+CD44+ALDH+ cells from UM-C4 colon tumors, TG cells fromother xenogeneic tumor lines (i.e. UM-C6, OMP-C5, and OMP-C8) did notco-purify with ALDH activity (FIG. 9C; Table 2), a result that mayreflect heterogeneity among patients, disease stage, the TG cell oforigin, and/or the repertoire of ALDH gene expression. Interestingly,the ALDH3A1 gene product may also mediate resistance to CPA, and itsexpression was uniquely elevated in microarray studies of UM-C4 TGversus NTG cells, but not differentially expressed in UM-C6 or UM-C9cells (FIGS. 10A & B). To validate microarray data, RNA wasindependently isolated from FACS-purified colon cancer stem cells andnon-tumorigenic cells, and relative gene expression was assessed usingTaqman assay quantitative RT-PCR. ALDH1A1 was validated as beingdramatically increased in TG versus NTG cells (FIG. 10C).

Cyclophosphamide (CPA) promotes DNA cross-linking and is a commonly usedchemotherapeutic agent, against which patients frequently developresistance. The elevated levels of ALDH and expression of a number ofALDH family member genes in TG colon tumor cells could contribute tosuch resistance in the very cells responsible for tumor recurrencepost-treatment. To test this, the resistance of TG cells from UM-C4tumors with high ALDH activity to CPA therapy compared to the majorityof NTG tumor cells (CD44^(neg) and/or ALDH^(neg)) was determined.Following tumor initiation with 500 ESA⁺CD44⁺ cells, tumors were allowedto reach ˜400 mm³, at which point the mice were randomized to receiveeither 25 mg/kg CPA or vehicle twice weekly. UM-C4 tumor growth inCPA-treated mice was retarded versus mice treated with vehicle (FIG.11A). Furthermore, ESA⁺CD44⁺ cells were more concentrated in tumors fromCPA-treated versus vehicle-treated mice (FIG. 11B) and the frequency ofcells with high ALDH activity was increased >70% (FIG. 11C), suggestingthat TG cells were truly more refractory to therapy than NTG cells.

To determine whether the increase in ESA⁺CD44⁺ALDH⁺ cells in CPA treatedtumors compared to control vehicle-treated controls correlated with anincrease in TG cell frequency, limiting doses of residual tumor tumorcells were transplanted into naïve NOD/SCID hosts. Specifically, todetermine the frequency of cancer stem cells in CPA-treated versusvehicle-treated animals, four sets of eight to more mice receivedtransplantation of 3-fold serial dilutions of bulk tumors cells,starting with 1,500 cells (dilutions: 1500, 500, 167 & 56 cells). Micewere monitored for tumor growth over a period of four months and scoredas either positive or negative for tumor growth such that Poissonstatistics could be done to assess TG cell frequency among the inputpopulation. All eight mice injected with 1,500 cells from eitherCPA-treated or vehicle-treated tumors developed tumors (Table 2). Inputof less cells clearly revealed an increased frequency of TG cells intumors from CPA-treated mice, as 9/9, 5/8 and 4/8 mice developed tumorswith an input of 500, 167 and 56 cell, respectively; whereas 6/8, 3/8and 2/8 mice grew tumors from serially transplanted vehicle-treatedtumors. These frequencies translated into a 1:120 versus 1:315 frequencyof TG cells in the bulk population of CPA-treated versus controlvehicle-treated tumors, demonstrating a >2.6-fold increase in TG cellsin CPA-treated tumors (FIG. 11D; p=0.024). Finally, though the inherentability of ESA⁺CD44⁺ cells to generate tumors appeared equal amongCPA-treated and vehicle-treated tumors, the data show a trend towardsmore aggressive tumor growth with cells sorted from CPA-treated tumors(FIG. 11E).

Example 12 Identification of Cancer Stem Cell Targets by Assessing InVivo Tumorigenicity

Cancer stem cells were maintained and expanded under in vitro cultureconditions as demonstrated by injection of those tumorigenic cancer stemcells into animals after being maintained in culture up to 14 days. Todetermine whether BMP receptor signaling has an effect on cancer stemcell expansion or maintenance in vitro, UM-C6 colon tumors wereprocessed, depleted of mouse lineage cells (mLin−; H2K^(d) and murineCD45), and plated on laminin-coated coverslips with media devoid of, orcontaining, 100 ng/mL of BMP2 and BMP4 for 6 days. Cells were thenharvested and injected subcutaneously into mice to determinetumorigenicity. Not only was tumorigenicity reduced (i.e. 83% vs 100%),but in contrast to various other agents (not discussed here), engagementof the BMP receptors in vitro significantly reduced the growth rate ofsubsequent tumors upon injection of these cells into mice (FIG. 12A).After more than 75 days in vivo, colon tumors derived from cells thathad been exposed to BMPs were 42.9±10% (N=5; p<0.002) the size ofcontrol tumors (FIG. 12B), demonstrating a detrimental effect ontumorigenicity.

Example 13 Isolation of Head and Neck Cancer Stem Cells

Using methods successfully employed to identify cancer stem cells inbreast cancer, head and neck squamous cell carcinoma (HNSCC) wasstudied. HNSCC contains a distinct population of cancer stem cells, withthe exclusive ability to produce tumors in mice and recreate theoriginal tumor heterogeneity. A cell surface marker that can distinguishthis cell population from the other cancer cells is present in thetumor. The ability to identify cancer stem cells in HNSCC allows for thedevelopment of new treatment strategies targeted against this criticalpopulation of cancer cells.

Primary tumor implantation. Female NOD/SCID mice were injectedintraperitoneally with ketamine/xylazine anesthetic at 0.02 mL/20-g (300mg ketamine combined with 20 mg xylazine in 4 mL of PBS). The freshtumor specimens on ice were received within an hour of extraction fromthe operating room in Media 199. Small pieces of tumor were chopped into2-mm size with scissors. Then a 3-mm incision was made in the mid backregion of the mice and small pieces of solid tumor were implanted inboth sides of the base of the neck with a trocar. Tumors were pinchedinto their final position in the mouse and the incision was sealed witha liquid adhesive suture.

Tumor Digestion. Primary tumors were cut into small fragments withsterile scissors and then further minced with sterile scalpels. Thepieces were then rinsed with HBSS (5 min: 1000 rpm) and placed in asolution of Media 199 and 200 u/mL Collagenase III. The mixture wasincubated at 37° C. for up to 3 hours to allow complete digestion. Every15 minutes, the solution was mixed through a 10-mL pipette to allowshearing of the tumor pieces. The digestion was arrested with theaddition of Fetal Bovine Serum and then filtered through a 40-μm-nylonmesh. The suspended cells were washed twice with Hank's Balanced SaltSolution/2% Heat Inactivated Calf Serum and then stained for flowcytometry, frozen, or injected.

Single cell suspension injections. The mice were anesthetized in thesame manner as the tumor implantation procedure. Up to 2 million cellswere washed in HBSS/2% HICS and then suspended in 100 μL of RPMI 1640.The cells were then mixed in a 1:1 ratio with Matrigel (BD Pharmingen)solution to form a final volume of 200 μL. The mice were then injectedsubcutaneously at the base of the neck with the suspension and thensealed with a liquid adhesive suture.

Flow Cytometry. The single cell suspensions were washed in HBSS/2% HICSand then the cells were counted. Cells were then resuspended in 100μL/10⁶ cells of HBSS and incubated with 1 mg/mL of Sandoglobin for 10minutes. The cells were then washed twice with HBSS/2% HICS, resuspendedin 100 μL/10⁶ cells of HBSS and stained with corresponding antibodies.Anti-CD44 (Pharred, PE or APC conjugated: BD Pharmingen) was added atthe appropriate dilution per antibody and incubated for 20 minutes onice. Primary tumor cells were also stained with lineage markersanti-CD2, CD3, CD10, CD16, CD18, CD31, CD64, and CD140b. Passaged tumorcells were incubated with anti-H2K^(d) (BD Pharmingen). Stained cellswere then washed 2 times with HBSS/HICS and resuspended at 0.5 mL/10⁶cells. 7-AAD (BD Pharmingen) was then added at the appropriate dilutionto allow for the removal of non-viable cells from the sort. Thissuspension was then sorted with a BD FACSVantage flow cytometer. AllLineage+/mouse cells were eliminated during flow cytometry. Dead cellswere removed based on positive 7-AAD staining. Forward and side scatterprofiles were utilized to remove cell doublets. All cells werereanalyzed and sorted twice to ensure purity of >95%.

HNSCC specimens were obtained from primary tumors in 4 differentsubjects. All tumors were successfully engrafted into the NOD/SCID mousemodel (Table 1). Three of the four experiments were conducted on tumorspecimens after they had been implanted and passaged in the mouse. Oneexperiment (UMHN4) was conducted on unpassaged tumor directly after itwas obtained from the patient. Contaminating mouse cells were removedfrom specimens passaged in the mouse by eliminating H2K⁺ cells (mousehistocompatibility class 1).

Identification of Tumorgenicity Markers. HNSCC specimens wereheterogeneous with respect to the cell surface marker CD44. To assesswhether CD44 could distinguish between tumorigenic and non-tumorigeniccells, flow cytometry was employed to isolate cells that were CD44positive or negative (CD44⁺, CD44⁻). When greater than 4×10⁴CD44⁺Lineage⁻ HNSCC cells were injected into the mice tumors alwaysformed within 12-16 weeks. When 5−25×10³ CD44⁺Lineage⁻ HNSCC cells wereinjected tumors formed in five out of eleven implantations. WhenCD44⁻Lineage⁻ cells were injected in all cases no detectable tumorsformed (Table 3). The one case where a tumor grew from CD44⁻ cellsoccurred early in the study and likely resulted from contamination ofthe sample with CD44+ cells, due to inexperience with the flow cytometrygating required for cell sorting.

Antigens associated with normal cell types (lineage markers CD2, CD3,CD10, CD18, CD31, CD64 and Q140b) were not expressed on the cancercells. These markers were used to eliminate normal leukocytes,fibroblasts endothelial, mesothelial and epithelial cells from the tumorspecimens. The percentage of CD44⁺Lineage⁻ cells in the tumors variedfrom 5.52 to 16.45 (FIG. 5A-D). As few as 5×10³ CD44⁺ cells gave rise totumors. In contrast up to 5×10⁵ CD44⁻ cells failed to form tumors. Evenafter greater than 24-32 weeks CD44⁻Lineage⁻ injection sites revealed nodetectable tumor growth.

The CD44⁺Lineage⁻ cells gave rise to tumors that contained cells thatwere phenotypically diverse for CD44 expression. Tumors resulting fromimplanted CD44⁺ cells reproduced the original tumor heterogeneity onhistologic examination (FIG. 6). Tumors grown from only CD44⁺ cellscould be resorted based on CD44 expression. CD44⁺ Lineage cells fromUMHN4 and SUHN2 were serially passaged through two rounds of tumorformation. CD44⁺Lineage⁻ cells from UMHN2 have been passaged throughthree rounds of tumor formation (FIG. 7). In each case only the CD44⁺cells produced tumor growth and the CD44⁻ population of cells did not.TABLE 3 Population Sample 500-650K 200-300K 100K 40-50K 20-25K 10K 5K 2KUMHN1 CD44+ 1/1 CD44− 0/1 UMHN2 CD44+ 2/2 1/1 CD44− 0/2 0/1 UMHN3 CD44+3/3 CD44− 0/3 0/3 0/3 UMHN4 CD44+ 1/1 CD44− 0/1

Example 14 Downstream Targets in Head and Neck Cancer Stem Cells

The methods used in this example provide guidance for the development ofNotch-related and other anti-cancer therapies using the cancer stemcells of the invention. Array technology is used to begin to understandthe molecular pathways that might be regulated by Notch-signalinginduced by specific Notch ligands. Sequence verified human cDNAs fromResearch Genetics, provided by the University of Michigan MicroarrayNetwork, are arrayed by the Cancer and Microarray Facility. Probes areprepared from self-renewing head and neck cancer stem cells or cellsfrom the various populations of cells found in a tumor. Probes arehybridized to the arrays and the hybridization patterns are read by theCancer and Microarray Facility. The hybridization patterns were thenanalyzed to identify genes that hybridize to probe from the head andneck cancer stem cells stimulated with various Notch ligands andnon-stimulated cells. Such genes can represent those that are involvedin the regulation of head and neck cancer cell survival or self-renewal.

Preparation of Microarrays. Microarray Technology was Used to AnalyzeGene expression of hematopoietic stem cells. This is now extended tocancer stem cells.

The University of Michigan Microarray Network currently has 32,500sequence verified human cDNAs from Research Genetics. A “cancer” chiphas been assembled in collaboration with the NCI. This chip contains acomprehensive constellation of 1,200 genes involved in proliferation andtumorigenesis. There is also an “apoptosis chip” developed by theUniversity of Michigan that contains all genes known to be involved inprogrammed cell death. Note that the HES genes, known to be downstreamtargets of Notch, are included in the arrays.

Preparation of Probe from Head and Neck Cancer Stem Cells. Messenger RNAis isolated either from freshly purified head and neck cancer stem cellsor from head and neck cancer stem cells incubated in the presence orabsence of various Notch ligands. The RNA is amplified if necessary,such as by PCR or linear RNA amplification Wang et al., NatureBiotechnology. 18:457-459 (April 2000). Probe are prepared by reversetranscription from an oligo-dT primer, and labeled by incorporating CY3or CY5 conjugated nucleotides. Gene expression profiles are examinedusing probe prepared from freshly isolated, uncultured head and neckcancer cells, as well as from cultured head and neck cancer cells, suchas cells that have been exposed to the appropriate Notch ligands(including Fringe family members, either singly or in combination asdetermined by which ligands are expressed by the different populationsof tumor cells. To do these assays, cells are exposed to a soluble formof Delta or Jagged family members in which the transmembrane region hasbeen deleted, or one of the Fringes. The Fringes are secreted proteins.Recombinant proteins are made of each Notch ligand of the Delta, Jaggedand Fringe families from insect cells or mammalian cells transfectedwith a baculovirus or mammalian expression vector, respectively.

Comparisons of gene expression patterns between control head and neckcancer tumorigenic cells and tumorigenic cells exposed to various Notchligands are made. Probe from head and neck cancer stem cells from eachtumor is combined with probe labeled with a different fluor made fromcultured head and neck cancer stem cells exposed to various Notchligands to compare their hybridization patterns. To do this, head andneck cancer stem cells are isolated by FACS. Cells are seeded at singlecell density to preclude Notch interactions between cells. Cells areexposed to soluble forms of Delta, Delta-like, Jagged 1, Jagged 2, oreach of the Fringes. Cells are exposed to each protein both alone and incombinations suggested by the Notch-ligand expression pattern ofindividual cell populations. The microarrays hybridized with probe fromeach test condition are compared and analyzed to gain insights intomolecular pathways affected by Notch ligand interactions. For example,if a particular population of cells expresses Delta and Manic Fringe,then one group of head and neck cancer stem cells is exposed to Deltaalone, a second to Delta and Manic Fringe and a third to Manic Fringealone. cDNA is made from each population with Cy5 or Cy3 labeling, andused to probe a microarray chip. In addition, cDNA from each populationis used with cDNA made from cells cultured in control medium and freshlyisolated head and neck cancer cells to probe a microarray chip. Eachgroup is compared 5 times to assure that any differences in expressionprofiles of the arrayed genes by each test groups are real.

Preparation of probe from cells treated with the anti-Notch 4 antibody.An antibody against Notch 4 inhibits growth in vitro and tumorigenesisin vivo. This effect can be explained if the antibody acts as either aNotch-4 agonist or antagonist. Since soluble Delta promotes cancer cellgrowth in vitro, the antibody most likely is a Notch 4 antagonist. Toconfirm the mechanism by which the anti-Notch 4 antibody inhibits tumorgrowth, probe is made from cells incubated in the presence or absence ofthe anti-Notch 4 or control irrelevant antibody and the variouscombinations of the Notch ligands and used for microarray expressionanalysis as described above. Another control group includes cellsincubated with the antibodies and no Notch ligand. Each comparison isperformed in at least six independent tests employing independentlyprepared batches of probe. By comparing the gene expression patterns ofeach group, how the anti-Notch 4 antibody affects Notch signaling can bedetermined.

Making the cDNA probe. 1-2 μg of mRNA is commonly used to synthesizeprobe for screening gene expression profiles on microarrays (Wang etal., Nature Biotechnology. 18:457-459 (April 2000)). 6 μg of mRNA isrequired per assay (reverse transcription of 6 μg of mRNA should yieldaround 3 μg of cDNA probe, or 1 μg of probe per slide). Cancer cellstend to have a high RNA content. In past assays, 107 cancer cellsyielded around 100 μg of total RNA, which in turn yielded around 3 jugof poly A⁺ RNA. Thus in order to generate 6 μg of mRNA, around 2×10⁷cells would be required. As described in the data, that number offlow-cytometrically purified head and neck cancer stem cells can beisolated from approximately five-ten 1 cm tumors.

The head and neck cancer stem cells represent approximately 5% of thetotal number of cells within a tumor. It is not practical to isolatemore than 10⁶ freshly dissociated (uncultured) head and neck cancer stemcells by flow-cytometry in one day. This would yield less than 0.5 μg ofmRNA from one day of sorting. While head and neck cancer stem cells canbe combined from multiple days of sorting to pool enough mRNA to prepareprobe from freshly isolated cells, it may not be practical to performall assays in this manner. Some assays require brief periods of tissueculture. Plating efficiency of the sorted cells is approximately 10%.Thus it may be necessary to enzymatically amplify the template prior tosynthesizing probe. This can be done either by PCR or by linearamplification of RNA using T7 RNA polymerase. The protocol employs 15-18rounds of PCR to amplify cDNA from small numbers of stem cells. Thisprotocol was used to construct a high quality hematopoietic stem cell(HSC) cDNA library and to make probe from hematopoietic stem cells. Toproduce probe from freshly isolated head and neck cancer stem cells, thesame approach is tested. Alternately, a number of groups have reportedsuccess in using linear RNA amplification to produce probe formicroarray hybridization. Thus, the two methods are compared bypreparing probe both ways and examining the hybridization patterns thatresult. cDNA is primed using an oligo-dT primer that contains a T7 RNApolymerase binding site and synthesized by Superscript reversetranscriptase (Gibco) and the Clontech 5's switch oligomer that allowsthe tagging of the 5′ end of the cDNA. Second strand cDNA is synthesizedusing E. coli DNA polymerase. Then amplified RNA (aRNA) is producedusing T7 RNA polymerase or PCR. Which of the two that amplificationmethods are used is determined by comparing probe made with standardcDNA synthesis. After preparing aRNA, cDNA is re-synthesized usingrandom hexamers. This cDNA can then be used for probe, or if necessary,additional rounds of amplification can be performed. Both approaches areused to prepare probe from 40,000 MCF-7 cells (a human breast cancerstem cell line). This probe is hybridized to human cDNA microarraysalong with probe from unamplified MCF-7 cells. The amplificationapproach that most closely reproduces the hybridization pattern of theunamplified probe is selected. Then amplification conditions aremodified until the amplified probe reproduces the hybridization patternof the unamplified probe as closely as possible.

Analysis of the hybridization pattern. Hybridization patterns areanalyzed in the Cancer and Microarray Core facility using their laserscanning system. The use of an integrated system for arraying,hybridizing, scanning, and analyzing hybridization patterns in which allcomponents are provided by Genomics Solutions permits a seamless andefficient analysis of hybridization patterns.

A transcript is differentially expressed if there is at least a 3-folddifference in normalized hybridization levels between probes.Hybridization signals from Cy3 and Cy5 labeled probes within a singletest are normalized to each other to correct for potential differencesin the effective concentration of each probe and replicates of each testare done using the opposite fluor for each group to correct fordifferences in the amounts or labeling efficiencies of probes.

Verification of differential expression. cDNAs that consistentlyhybridize to probe from groups of cells but not to probe from thecontrol groups of cells are further characterized. The sequences ofthese cDNAs are obtained from the Microarray Network. Two approaches areused to confirm the differential expression of candidate genes betweencell populations. The first is to prepare in situ hybridization probesagainst candidate genes, and then perform in situ hybridizations on headand neck cancer stem cells cultured in medium with or without variousNotch ligands as described above. In situ hybridizations are thenperformed on cultured cells. The advantage of this approach would bethat expression could be compared at the level of individual cells.

An alternate approach is to design nested PCR primers against candidategenes, and to perform RT-PCR on multiple 1-10-cell aliquots of freshlypurified head and neck cancer stem cells (isolated as described above).By performing RT-PCR on small numbers of cells it is possible to observea difference in the ability to amplify particular transcripts, even ifthe “non-expressing” population contains rare expressing cells. Thisapproach was used to demonstrate the differential expression of RGS 18between different subpopulations of multipotent hematopoieticprogenitors.

Differential expression can be confirmed by Northern analysis. Poly A⁺RNA from 1−2×10⁷ head and neck cancer stem cells cultured with orwithout the Notch ligands, are hybridized to probes of thedifferentially expressed cDNAs. Hybridization signals are quantitativelycompared between these samples.

Confirmation that genes are differentially expressed at the proteinlevel is then performed. In cases where immunocytochemical staining isuninformative, western blots on protein from the different cells areperformed.

Certain molecular analyses are difficult using the primary head and neckcancer cells that only proliferate for prolonged periods of time in thexenograft model. These analyses can be done in cell lines. Any of alarge number of head and neck cancer cell lines can be used. Clarke etal., Proc. Natl. Acad. Sci. USA. 92:11024-28 (November 1995);Hernandez-Alcoceba et al., Human Gene Therapy. 11:20 (September 2000).These cell lines are plated at single-cell density with and withoutvarious Notch ligands, as well as the anti-Notch 4 or control antibodiesas described in the assays with the primary head and neck cancer cells.If clonogenicity is affected by Notch signaling, then probe for themicroarray analysis is made using cDNA made form the cell line incubatedin medium with or without the various Notch ligands or anti Notch 4 orcontrol antibodies. Since a virtually unlimited number of cells can beanalyzed, a probe can be made that has not been amplified.

Finally, cell lines are useful for confirming whether the anti-Notch 4antibody is an agonist or antagonist. If a cell line is identified thatclonogenicity is enhanced by soluble Delta and inhibited by theanti-Notch 4 antibody, then it is used in these assays. The cells arestably transfected with a luciferase minigene under the control of theNotch-inducible HES-1 promoter. Jarriault et al., Molecular & CellularBiology 18:7423-31 (1998). The cells are plated at single cell densityto prevent cell-cell Notch-Notch ligand interactions. They are treatedwith the various combinations of Notch ligands and either the anti-Notch4 antibody or a control antibody. The cells are harvested and aluciferase assay is done to determine how each condition affects Notchsignal transduction as reflected by transactivation of the HET1promoter.

A comprehensive functional analysis of candidate genes that emerge fromthe microarray analysis can be performed. Full-length cDNAs are isolatedand cloned into a retroviral expression vector. Head and neck cancercell lines and head and neck cancer stem cells isolated from the fivexenograft tumors are infected in vitro and the effect of the retroviraltransgene on self-renewal and tumorigenicity is assayed relative toclones infected with a control vector. The transgene is expressed as abicistronic message that contains IRES-GFP. This allows identificationof transduced cells via FACS or fluorescent microscopy. The effect ofthe transgene on Notch signaling is examined in vitro and in vivo. To dothis, transduced cells are tested for response to the variouscombinations of Notch ligands found to affect colony formation in tissueculture and tumorigenicity in mice.

The expression patterns of candidate genes are examined in detail invivo to determine how widely the genes are expressed beyond thexenograft. In addition to performing more extensive in situhybridizations of tissue sections from slices of primary head and neckcancer, antibodies against selected gene products being studied can bemade. The Hybridoma Core facility at the University of Michigan hasextensive experience preparing monoclonal antibodies using bothpeptides, and expressed recombinant proteins.

Ultimately, the functions of unknown genes are tested in vivo, usinggene targeting to make knockout mice. The University of MichiganTransgenic Core has established murine ES cell technology, they provideES cells that “go germline” at a high rate and assist with thegeneration of homologous recombinant ES clones.

The ability of microarray analysis to simultaneously compare theexpression of many genes provides unparalleled power to screen forchanges in gene expression patterns. Combined with the ability to purifystem cells and to regulate their self-renewal and differentiation invitro, microarray analyses can be applied with great precision to screenfor specific types of regulatory genes.

Example 15 Cancer Stem Cells as a Side Population

Certain stem cell populations, including hematopoietic stem cells (HSC),have the ability to efflux a fluorescent dye (e.g. Hoechst 33342) andcorrespond to a “side population” of cells (Goodell M A, Brose K,Paradis G, Conner A S, Mulligan R C. J Exp Med. (1996) 183:1797-1806;Kim M, Turnquist H, Jackson J, et al. Clin Cancer Res. (2002) 8:22-28;Scharenberg C W, Harkey M A, Torok-Storb B., Blood (2002) 99:507-512;Zhou S, Morris J J, Barnes Y, Lan L, Schuetz J D, Sorrentino B P. ProcNatl Acad Sci USA. (2002) 99:12339-44). To determine whether tumorigenicstem cells are enriched in a side population (SP) of cells, PE13 andUMC4 tumor cells were labeled with Hoechst 33342 for 30 minutes at 37°C., followed by incubation, wherein cells can actively efflux the dye ifthey have high efflux activity. Following Hoechst 33342 labeling andefflux incubations, cells were labeled with ESA-FITC and CD44-APC so thephenotype of SP cells might be identified. In both breast PE13 and colonUMC4 tumors, SP cells were highly enriched for ESA⁺CD44⁺ cells (FIG.14A).

To determine whether tumorigenicity was also maintained, or evenenriched in SP versus non-SP ESA⁺CD44⁺ cells, various populations wereisolated by FACS and injected into mice. While the SP population wasenriched for tumorigenic cells, SP did not exclusively parsetumorigenic, and ESA⁺CD44⁺ cells from SP or non-SP were equallytumorigenic, demonstrating the greatest association of tumorigenicitywith the ESA⁺CD44⁺ phenotype. Thus, isolation of SP provides a mechanismfor the partial enrichment of cancer stem cells. Of note, tumors fromcells sorted using the SP protocol arose with longer latency and lessfrequency, thus it is likely that some toxicity was associated with SPcell procurement, possibly due to the Hoechst staining protocol or thebrief violet laser exposure during FACS.

Microarray studies using mRNA from tumorigenic versus non-tumorigeniccolon tumor populations isolated by FACS showed differential expressionby a number of ABC family transporters (FIG. 14B), believed to beresponsible for the efflux ability of the SP (Alison M R. J. Pathol.(2003) 200:547-550; Glavinas H, Krajcsi P, Cserepes J, Sarkadi B., CurrDrug Deliv. (2004) 1:27-42. Some, such as ABCD3 and ABCE1, weresignificantly higher in the tumorigenic population, whereas others (e.g.ABCC3) were more highly expressed in non-tumorigenic tumor cells.Differential expression of ABC family transporters on cancer stem cellsor non-tumorigenic tumor cells can be utilized in prognostic ortherapeutic applications.

Example 16 CD59 Enriches for Colon Cancer Stem Cells

CD59 mRNA was identified as being significantly overexpressed intumorigenic versus nontumorigenic cells from colon tumors UMC4 and UM-C6by microarray analysis (FIG. 15A). Flow cytometry also demonstrated thatthe TG ESA⁺CD44⁺ population expressed higher levels of surface CD59protein than the remaining non-tumorigenic tumor populations (FIG. 15B).This was most pronounced in UM-C6 tumor cells, where CD59 cleanlydistinguished CD44⁺ cells from non-tumorigenic CD44⁻ cells, therebysuggesting its value as a marker for enriching cancer stem cells in sometumor samples. In an attempt to determine whether CD59 expression mightidentify a NTG population among ESA⁺CD44⁺ cells of colon tumors, therebyalso allowing further enrichment of TG colon cancer stem cells, primaryxenograft tumors were depleted of murine cells (Lineage-depleted), andsubpopulations of ESA⁺CD44⁺ cells were isolated by FACS based on CD59expression (FIG. 15B). In UMC4 cells, CD59^(hi) cells generally alsohave higher surface expression of CD29 (β1-integrin), another moleculediscovered to be more highly expressed at mRNA level in TG colon cancerstem cells by microarray studies and confirmed at the protein level withFACS analysis.

An experiment with UMC4, demonstrated a correlation between CD59 andxenogeneic tumor engraftment/growth in the ESA⁺CD44⁺ population (FIG.15C & Table 4). TABLE 4 Tumors/Injections UMC4 200 100 ESA⁺CD44⁺CD49f⁺5/5 5/10 ESA⁺CD44⁺CD49f⁻ 2/5 2/10 ESA⁺CD44⁻ 0/5 — UMC4 500ESA⁺CD44⁺GD59⁺ 13/14 — ESA⁺CD44⁺CD59⁻ 5/7 — ESA⁺CD44⁻ 0/4 —

13/14 mice injected with CD59^(int/high) ESA⁺CD44⁺ cells developedtumors that rapidly grew to over 2,000 cm². Only 4/7 tumors withCD59^(low) ESA⁺CD44⁺ cells developed, and those that did grow, grew moreslowly than those tumors that developed with CD59^(int/hi) cells. 0/4tumors grew larger than 200 cm² (only 1 had any growth, but regressedafter 5 weeks) with ESA⁺CD44⁻ cells. The correlation between CD59 andengraftment/growth can reflect a couple of possibilities: a) CD59protects cells from death or host immunosurveillence and thus tumorshave a better chance of developing, and/or b) CD59 demarcates thetumorigenic subset of ESA+CD44+ cells in UMC4 tumors. It should be notedthat the “spread” of CD59 expression was not wide, but couldnevertheless prove useful. All resulting tumor phenotypes in this studylooked normal (˜9-15% ESA+CD44+).

Example 17 CD49 Enriches for Colon Cancer Stem Cells

CD49 mRNA was identified as being significantly overexpressed intumorigenic versus nontumorigenic cells from colon tumors UMC4 and UM-C6by microarray analysis. In an attempt to determine whether CD59expression might identify a NTG population among ESA⁺CD44⁺ cells ofcolon tumors, thereby also allowing further enrichment of TG coloncancer stem cells, primary xenograft tumors were depleted of murinecells (Lineage-depleted), and subpopulations of ESA⁺CD44⁺ cells wereisolated by FACS based on CD49 expression (FIG. 16A). An experiment withUMC4, demonstrated a correlation between CD49 and xenogeneic tumorengraftment/growth in the ESA⁺CD44⁺ population (FIG. 16B & Table 4).

All publications and patents cited herein are incorporated by referenceherein in entirety. Various modifications and variations of thedescribed method and system of the invention will be apparent to thoseskilled in the art without departing from the scope and spirit of theinvention. Although the invention has been described in connection withspecific embodiments, it should be understood that the invention asclaimed should not be unduly limited to such specific embodiments.Indeed, various modifications of the described modes for carrying outthe invention that are obvious to those skilled in the relevant fieldsare intended to be within the scope of the following claims.

1. An isolated population of cancer stem cells obtained from a tumor ofepithelial origin, wherein the population comprises at least 75% cancerstem cells and less than 25% non-tumorigenic tumor cells, wherein thecancer stem cells: are tumorigenic; and, express elevated levels of oneor more of PTGFRN, CD166, CD164, CD82, TGFBR1, MET, EFNB2, ITGA6, TDGF1,HBEGF, ABCC4, ABCD3, TDE2, ITGB1, TNFRSF21, CD81, CD9, KIAA1324,CEACAM6, FZD6, FZD7, BMPR1A, JAG1, ITGAV, NOTCH2, SOX4, HES1, HES6,ATOH1, CDH1, EPHB2, MYB, MYC, SOX9, PCGF1, PCGF4, PCGF5, ALDH1A1, andSTRAP, or reduced levels of one or both of TCF₄ or VIM relative to thenon-tumorigenic tumor cells.
 2. The isolated population of cancer stemcells of claim 1, wherein the cancer stem cells are CD44+.
 3. Theisolated population of cancer stem cells of claim 1, wherein the cancerstem cells further express epithelial specific antigen (ESA).
 4. Theisolated population of cancer stem cells of claim 1, wherein the cancerstem cells are colon cancer stem cells.
 5. The isolated population ofcancer stem cells of claim 1, wherein the cancer stem cells are head andneck cancer stem cells.
 6. An enriched population of cancer stem cellsobtained from a tumor of epithelial origin, wherein the populationcomprises cancer stem cells and non-tumorigenic tumor cells, wherein thecancer stem cells: are enriched at least two-fold compared tounfractionated non-tumorigenic tumor cells; are tumorigenic; and expresselevated levels of one or more of PTGFRN, CD166, CD164, CD82, TGFBR1,MET, EFNB2, ITGA6, TDGF1, HBEGF, ABCC4, ABCD3, TDE2, ITGB1, TNFRSF21,CD81, CD9, KIAA1324, CEACAM6, FZD6, FZD7, BMPR1A, JAG1, ITGAV, NOTCH2,SOX4, HES1, HES6, ATOH1, CDH1, EPHB2, MYB, MYC, SOX9, PCGF1, PCGF4,PCGF5, ALDH1A1, and STRAP, or reduced levels of one or both of TCF4 orVIM relative to the non-tumorigenic tumor cells.
 7. The enrichedpopulation of cancer stem cells of claim 6, wherein the cancer stemcells are CD44+.
 8. The enriched population of cancer stem cells ofclaim 6, wherein the cancer stem cells further express epithelialspecific antigen (ESA).
 9. The enriched population of cancer stem cellsof claim 6, wherein the cancer stem cells are colon cancer stem cells.10. The enriched population of cancer stem cells of claim 6, wherein thecancer stem cells are head and neck cancer stem cells.
 11. A method forobtaining from a tumor a cellular composition comprising cancer stemcells and non-tumorigenic tumor cells, wherein at least 75% aretumorigenic stem cells and 25% or less are non-tumorigenic tumor cells,said method comprising: (a) obtaining a dissociated mixture of tumorcells from a tumor of epithelial origin; (b) separating the mixture oftumor cells into a first fraction comprising at least 75% cancer stemcells and 25% or less non-tumorigenic tumor cells and a second fractionof tumor cells depleted of cancer stem cells wherein the separating isby contacting the mixture with reagents against CD44 and ESA; and (c)demonstrating the first fraction to be tumorigenic by serial injectioninto a first host animal and the second fraction to be non-tumorigenicby serial injection into a second host animal.
 12. The method of claim11 wherein the separating is performed by flow cytometry, fluorescenceactivated cell sorting (FACS), panning, affinity chromatography ormagnetic selection.
 13. The method of claim 11 wherein the separating,is performed by fluorescence activated cell sorters (FACS) analysis. 14.The method of claim 11 wherein the cancer stem cells are colon cancerstem cells.
 15. The method of claim 11 wherein the cancer stem cells arehead and neck cancer stem cells.
 16. A method for enriching a populationof cancer stem cells from a tumor of epithelial origin wherein theenriched population comprises 75% cancer stem cells and 25% or lessnon-tumorigenic tumor cells, said method comprising: (a) obtaining adissociated mixture of tumor cells from a tumor of epithelial origin;(b) contacting the mixture of tumor cells with reagents against CD44 andESA; (c) selecting a first fraction of cancer stem cells by theirbinding to the reagents and a second fraction of colon tumor cellsdepleted of colon cancer stem cells; and (d) demonstrating the firstfraction to be tumorigenic by serial injection of the colon tumor stemcells into a host animal and the second fraction to be non-tumorigenicby serial injection into the host animal.
 17. The method of claim 16wherein the selecting is performed by flow cytometry, fluorescenceactivated cell sorting (FACS), panning, affinity chromatography, ormagnetic selection.
 18. The method of claim 16 wherein the selecting isperformed by fluorescence activated cell sorters (FACS) analysis. 19.The method of claim 16 wherein the cancer stem cells are colon cancerstem cells.
 20. The method of claim 16 wherein the cancer stem cells arehead and neck cancer stem cells.
 21. An isolated population of cancerstem cells obtained from a tumor of epithelial origin, wherein thepopulation comprises at least 75% cancer stem cells and less than 25%tumor cells, wherein the cancer stem cells: are tumorigenic; are CD44+;and display elevated levels of ALDH activity; and wherein the tumorcells are non-tumorigenic.
 22. The isolated population of colon cancerstem cells of claim 21, wherein the colon cancer stem cells furtherexpress epithelial specific antigen (ESA).
 23. The isolated populationof cancer stem cells of claim 21, wherein the cancer stem cells arecolon cancer stem cells.
 24. The isolated population of cancer stemcells of claim 21 wherein the cancer stem cells are head and neck cancerstem cells.
 25. An enriched population of cancer stem cells obtainedfrom a tumor of epithelial origin, wherein the population comprisescancer stem cells and tumor cells, wherein the colon cancer stem cells:are enriched at least two-fold compared to unfractionated tumor cells;are tumorigenic; are CD44+; and display elevated levels of ALDHactivity; and wherein the tumor cells are non-tumorigenic.
 26. Theenriched population of colon cancer stem cells of claim 25, wherein thecolon cancer stem cells further express epithelial specific antigen(ESA).
 27. The enriched population of cancer stem cells of claim 25,wherein the cancer stem cells are colon cancer stem cells.
 28. Theenriched population of cancer stem cells of claim 25, wherein the cancerstem cells are head and neck cancer stem cells.
 29. A method ofidentifying the presence of cancer stem cells in a subject suspected ofhaving cancer, wherein the method comprises: (a) obtaining a biologicalsample from the subject; (b) dissociating cells of the sample; (c)contacting the dissociated cells with a first reagent that binds CD44and a second reagent that binds CD166; and (d) detecting cancer stemcells that bind to the first and second reagent.
 30. The method of claim29, wherein the first or second reagent is an antibody.
 31. The methodof claim 29, wherein the detection step is performed by flow cytometry,fluorescence activated cell sorting, panning, affinity columnseparation, or magnetic selection.
 32. The method of claim 29 whereinthe cancer stem cells are colon cancer stem cells.
 33. The method ofclaim 29 wherein the cancer stem cells are head and neck cancer stemcells.
 34. A method of identifying the presence of cancer stem cells ina subject suspected of having cancer, wherein the method comprises: (a)obtaining a biological sample from the subject; (b) dissociating cellsof the sample; (c) contacting the dissociated cells with a first reagentthat binds CD44 and a second reagent that detects ALDH activity; and (d)detecting cancer stem cells that bind to the first reagent and that showincreased ALDH activity.
 35. The method of claim 34, wherein the firstreagent is an antibody.
 36. The method of claim 34, wherein thedetection step is performed by flow cytometry, fluorescence activatedcell sorting, panning, affinity column separation, or magneticselection.
 37. The method of claim 34 wherein the cancer stem cells arecolon cancer stem cells.
 38. The method of claim 34 wherein the cancerstem cells are head and neck cancer stem cells.
 39. An isolatedpopulation of cancer stem cells obtained from a tumor of epithelialorigin, wherein the population comprises at least 75% cancer stem cellsand less than 25% tumor cells, wherein the cancer stem cells: aretumorigenic; are CD44+; and display elevated levels of CD49f activity;and wherein the tumor cells are non-tumorigenic.
 40. The isolatedpopulation of colon cancer stem cells of claim 39, wherein the coloncancer stem cells further express epithelial specific antigen (ESA). 41.The isolated population of cancer stem cells of claim 39, wherein thecancer stem cells are colon cancer stem cells.
 42. The isolatedpopulation of cancer stem cells of claim 39 wherein the cancer stemcells are head and neck cancer stem cells.
 43. An enriched population ofcancer stem cells obtained from a tumor of epithelial origin, whereinthe population comprises cancer stem cells and tumor cells, wherein thecolon cancer stem cells: are enriched at least two-fold compared tounfractionated tumor cells; are tumorigenic; are CD44+; and displayelevated levels of CD49f activity; and wherein the tumor cells arenon-tumorigenic.
 44. The enriched population of colon cancer stem cellsof claim 43, wherein the colon cancer stem cells further expressepithelial specific antigen (ESA).
 45. The enriched population of cancerstem cells of claim 43, wherein the cancer stem cells are colon cancerstem cells.
 46. The enriched population of cancer stem cells of claim43, wherein the cancer stem cells are head and neck cancer stem cells.47. A method of identifying the presence of cancer stem cells in asubject suspected of having cancer, wherein the method comprises: (a)obtaining a biological sample from the subject; (b) dissociating cellsof the sample; (c) contacting the dissociated cells with a first reagentthat binds CD44 and a second reagent that binds CD49f, and (d) detectingcancer stem cells that bind to the first and second reagent.
 48. Themethod of claim 47, wherein the first or second reagent is an antibody.49. The method of claim 47, wherein the detection step is performed byflow cytometry, fluorescence activated cell sorting, panning, affinitycolumn separation, or magnetic selection.
 50. The method of claim 47wherein the cancer stem cells are colon cancer stem cells.
 51. Themethod of claim 47 wherein the cancer stem cells are head and neckcancer stem cells.
 52. An isolated population of cancer stem cellsobtained from a tumor of epithelial origin, wherein the populationcomprises at least 75% cancer stem cells and less than 25% tumor cells,wherein the cancer stem cells: are tumorigenic; are CD44+; and displayelevated levels of CD59 activity; and wherein the tumor cells arenon-tumorigenic.
 53. The isolated population of colon cancer stem cellsof claim 52, wherein the colon cancer stem cells further expressepithelial specific antigen (ESA).
 54. The isolated population of cancerstem cells of claim 52, wherein the cancer stem cells are colon cancerstem cells.
 55. The isolated population of cancer stem cells of claim 52wherein the cancer stem cells are head and neck cancer stem cells. 56.An enriched population of cancer stem cells obtained from a tumor ofepithelial origin, wherein the population comprises cancer stem cellsand tumor cells, wherein the colon cancer stem cells: are enriched atleast two-fold compared to unfractionated tumor cells; are tumorigenic;are CD44+; and display elevated levels of CD59 activity; and wherein thetumor cells are non-tumorigenic.
 57. The enriched population of coloncancer stem cells of claim 56, wherein the colon cancer stem cellsfurther express epithelial specific antigen (ESA).
 58. The enrichedpopulation of cancer stem cells of claim 56, wherein the cancer stemcells are colon cancer stem cells.
 59. The enriched population of cancerstem cells of claim 56, wherein the cancer stem cells are head and neckcancer stem cells.
 60. A method of identifying the presence of cancerstem cells in a subject suspected of having cancer, wherein the methodcomprises: (a) obtaining a biological sample from the subject; (b)dissociating cells of the sample; (c) contacting the dissociated cellswith a first reagent that binds CD44 and a second reagent that bindsCD59; and (d) detecting cancer stem cells that bind to the first andsecond reagent.
 61. The method of claim 60, wherein the first or secondreagent is an antibody.
 62. The method of claim 60, wherein thedetection step is performed by flow cytometry, fluorescence activatedcell sorting, panning, affinity column separation, or magneticselection.
 63. The method of claim 60 wherein the cancer stem cells arecolon cancer stem cells.
 64. The method of claim 60 wherein the cancerstem cells are head and neck cancer stem cells.
 65. The isolatedpopulation of cancer stem cells of claim 1, wherein the cancer stemcells express elevated levels of one or more of PTGFRN, CD166, CD164,CD82, TGFBR1, MET, EFNB2, ITGA6, TDGF1, HBEGF, ABCC4, ABCD3, TDE2,ITGB1, TNFRSF21, CD81, CD9, KIAA1324, CEACAM6, FZD6, FZD7, BMPR1A, JAG1,ITGAV, NOTCH2, SOX4, HES6, relative to the non-tumorigenic tumor cells.66. The isolated population of cancer stem cells of claim 1, wherein thecancer stem cells express elevated levels of one or more of HES1, ATOH1,CDH1, EPHB2, MYB, MYC, SOX9 and STRAP, or reduced levels of one or bothof TCF4 or VIM, relative to the non-tumorigenic tumor cells.
 67. Theenriched population of cancer stem cells of claim 6, wherein the cancerstem cells express elevated levels of one or more of PTGFRN, CD166,CD164, CD82, TGFBR1, MET, EFNB2, ITGA6, TDGF1, HBEGF, ABCC4, ABCD3,TDE2, ITGB1, TNFRSF21, CD81, CD9, KIAA1324, CEACAM6, FZD6, FZD7, BMPR1A,JAG1, ITGAV, NOTCH2, SOX4, HES6, relative to the non-tumorigenic tumorcells.
 68. The enriched population of cancer stem cells of claim 6,wherein the cancer stem cells express elevated levels of one or more ofHES1, ATOH1, CDH1, EPHB2, MYB, MYC, SOX9 and STRAP, or reduced levels ofone or both of TCF4 or VIM, relative to the non-tumorigenic tumor cells.